Test framework and jshint adjustments
We don't even use grunt for testing
Testing constructor.
Testing new Constructor API (tests are obviously failing)
Handling images in fixtures

Conflicts:
	test/unit/core.js
Removing $ from the global namespace to avoid conflicting with the internal dollar and tests

Conflicts:
	test/unit/core.js
Testing new `data-src` syntax.

- initial tests are failing because the old feature is still working (good way to know the old expectation we are going to break)
- new tests are  not working because basically it's not done yet
regex -> {width}

- removed Imager `regex` option
- implemented simple `{width}` interpolation
Pixel ratio tests
Pixel ratio implementation

- added Imager.transforms to let room to customise things further on
- replacing {pixel_ratio} pattern in `data-src` URI
add CH-DPR hint