Add CSS linting; add Component(1) for dev
Add 'suit-test' as a development dependency
Update Bower ignores
Use 'suit-test' to structure the visual tests

Adds new tests for 'iframe' and 'tabindex=-1'.
Add `!important` to the tabindex rule

This style should apply irrespective of the specificity of other rules,
e.g., `:focus` rules applied in SUIT components.
Add Makefile
Update the README with testing information
Update CHANGELOG
v0.3.0