Merge pull request #96 from mfairchild365/alpha-index

Mark contrast errors with alpha transparency as warnings
Merge remote branch 'grunt/master'
Pull in a Grunt PR and move it into a new Contrib dir.

1. Merge pull request #83 from 'yargalot/master'.
   But:
   - Moved it into a Contrib/Grunt dir, setting base inside file.
     This will require calling grunt either with
--gruntfile=Contrib/Grunt/gruntfile.coffee.
   - Changed the version number to 2.0.1.
2. PhantomJS can live in there too.
More cleanups for Grunt setup.

1. Move package.json back to top level so if for some reason it gets
packaged into a nodejs module it's in the right place. Gruntfile changed
to suit.
2. Remove unnecessary files from the top level.
Ensure the licence.txt gets included with any build
Add methods to convert an rgba background color to rgb
Convert rgba to a solid color before checking contrast
Don't warn about rgba anymore

No need to, we are doing the maths!
Convert to a colour string

The rest of the code expects bgColour to be a string
Return rgb channels as %

Everything else expects them as %.  Also, rework to reduce rounding problems.
Allow checking against any rgba color, not just the background
Also convert the foreground (text) rgba color
Merge remote-tracking branch 'squizlabs/master' into alpha-checking
Correctly calculate layered transparencies

Take this structure of backgrounds for example, 1 being the closest element:
1. rgba(10,10,10, .5);
2. rgba(10,10,50, .1);
3. rgb(10,10,250);

We need to transform background 2 into a solid color before we transform background 1 into a solid colour.
Allow implicit labels to provide a name for input

This follows the test procedure from http://www.w3.org/TR/2014/NOTE-WCAG20-TECHS-20140408/F68
Merge remote-tracking branch 'kabel/feature-implicit-labels'
Assume a white background if no solid colors were found
Include an alpha
Merge branch 'alpha-checking'
Make absolutely positioned contrast errors warnings

We can't reliably compute the contrast of text over a background if the text is absolutely positioned over the background of another element that isn't a direct parent of the text element.