Fix JSHint errors

[rexagod]

Fixes #100, however, it must be noted that after merging jywarren:fullres-dl to master on local I found that 3 tests are failing now.

Current Logs

▶ grunt build
Running "jshint:source" (jshint) task
>> 11 files lint free.

Running "jshint:grunt" (jshint) task
>> 1 file lint free.

Running "karma:development:start" (karma) task

START:
08 02 2019 21:10:29.228:INFO [karma-server]: Karma v3.1.4 server started at http://0.0.0.0:9876/
08 02 2019 21:10:29.256:INFO [launcher]: Launching browsers PhantomJS with concurrency unlimited
08 02 2019 21:10:29.374:INFO [launcher]: Starting browser PhantomJS
08 02 2019 21:10:30.334:INFO [PhantomJS 2.1.1 (Linux 0.0.0)]: Connectedon socket 8I7ht8H7lPFfLS3JAAAA with id 31845357
  L.DistortableImageOverlay
    #_calculateProjectiveTransform
      ✖ Should (skipped)
08 02 2019 21:10:31.116:WARN [web-server]: 404: /base/examples/example.jpg
    getCenter
      ✖ Should return the center when the outline of the image is a rectangle.
08 02 2019 21:10:33.096:WARN [web-server]: 404: /base/examples/example.jpg
  L.DistortableImage.Edit
    ✖ "before each" hook for "Should be initialized along with each instance of L.DistortableImageOverlay."
08 02 2019 21:10:35.136:WARN [web-server]: 404: /base/examples/example.jpg
  L.RotateHandle
    ✖ "before each" hook for "Should return 0 when given the same latlng twice."
  L.DomUtil
    .getMatrixString
      ✔ Should
  L.MatrixUtil
    .multmm
      ✔ Should act as the identity when the identity matrix is on the left.
      ✔ Should act as the identity when the identity matrix is on the right.
    .multsm
      ✔ Should scale the identity matrix.
    .general2DProjection
      ✔ Should return the 3*3 identity matrix when each corner is mapped back to itself.
      ✔ Should return a scalar multiple of the 3*3 identity matrix whenthe image is scaled.

Finished in 6.255 secs / 6.037 secs @ 21:10:37 GMT+0530 (IST)

SUMMARY:
✔ 6 tests completed
ℹ 1 test skipped
✖ 3 tests failed

FAILED TESTS:
  L.DistortableImageOverlay
    getCenter
      ✖ Should return the center when the outline of the image is a rectangle.
        PhantomJS 2.1.1 (Linux 0.0.0)
      Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

  L.DistortableImage.Edit
    ✖ "before each" hook for "Should be initialized along with each instance of L.DistortableImageOverlay."
      PhantomJS 2.1.1 (Linux 0.0.0)
    Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

  L.RotateHandle
    ✖ "before each" hook for "Should return 0 when given the same latlng twice."
      PhantomJS 2.1.1 (Linux 0.0.0)
    Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

Warning: Task "karma:development:start" failed. Use --force to continue.

Aborted due to warnings.

Logs @ #127

▶ grunt build
Running "jshint:source" (jshint) task
>> 11 files lint free.

Running "jshint:grunt" (jshint) task
>> 1 file lint free.

Running "karma:development:start" (karma) task

START:
06 02 2019 16:45:54.868:INFO [karma-server]: Karma v3.1.4 server started at http://0.0.0.0:9876/
06 02 2019 16:45:54.870:INFO [launcher]: Launching browsers PhantomJS with concurrency unlimited
06 02 2019 16:45:54.890:INFO [launcher]: Starting browser PhantomJS
06 02 2019 16:45:58.299:INFO [PhantomJS 2.1.1 (Linux 0.0.0)]: Connected on socket LpERJgPzRtZzNKSWAAAA with id 70904612
  L.DistortableImageOverlay
    #_calculateProjectiveTransform
      ✖ Should (skipped)
    getCenter
      ✔ Should return the center when the outline of the image is a rectangle.
  L.DistortableImage.Edit
    ✔ Should be initialized along with each instance of L.DistortableImageOverlay.
    ✔ Should keep handles on the map in sync with the corners of the image.
    ✖ Should keep image in sync with the map while dragging. (skipped)
  L.RotateHandle
    _calculateRotation
      ✔ Should return 0 when given the same latlng twice.
    _calculateScalingFactor
      ✔ Should return 1 when given the same latlng twice.
  L.DomUtil
    .getMatrixString
      ✔ Should
  L.MatrixUtil
    .multmm
      ✔ Should act as the identity when the identity matrix is on the left.
      ✔ Should act as the identity when the identity matrix is on the right.
    .multsm
      ✔ Should scale the identity matrix.
    .general2DProjection
      ✔ Should return the 3*3 identity matrix when each corner is mapped back to itself.
      ✔ Should return a scalar multiple of the 3*3 identity matrix when the image is scaled.

Finished in 0.159 secs / 0.096 secs @ 16:45:58 GMT+0530 (IST)

SUMMARY:
✔ 11 tests completed
ℹ 2 tests skipped

Running "coverage" task

Running "concat:dist" (concat) task

Done.

[jywarren]

Pulled into #100, thanks!!!