Add Blanket JS support for code coverage

To run it: `bundle exec rake jasmine:blanketjs`
Info on how to run tests, including coverage tests
Make code coverage env variable name more explicit
Merge branch 'js-code-coverage' of github.com:alphagov/limelight into js-code-coverage
Add jshint support and sample config
Add info on how to run jshint
Exclude vendor from jshint checks
Do not complain about jquery and require vars
Ignore underscore var for jshint
Allow use of '== null'
Merge pull request #195 from alphagov/js-code-coverage

Js code coverage and jshint
no baseline-shift because only chrome supports it properly
just bump the y number for now
Force dig-uptake number to 1 decimal place
Decrease size to allow larger number
Make impact numbers match
Fix all the tests
Merge pull request #197 from alphagov/dig-takeup-tweaks

Dig takeup tweaks
change value labels to use bounding box height to inform their positions
add getNodeHeight method and run spec against it