Refine docs

- Fixes #488
Add validate-length function
Add validate-size function
Refactor size addon

- Allow auto, inherit, initial values
- Allow unitless number values
- Allow intrinsic sizing values
- Fixes #391
- Fixes #468
Remove triple asterisk from README
Imports font-source-declaration helper
Adds ability to target :active pseudo-class for $all-text-inputs
Refactors contains functions

- Supports LibSass
- Closes #587
Refactors is-num function

- Closes #584
Fixes bug in the new font-face mixin

- Fix format of ttf files to truetype
- Remove EOT src that didn’t have iefix query
- Use double quotes
- Fixes #594
Library details refinements
Changes comment style for info in manifest