Remove Checkbox Hover, Escape Less Relative Path

- less/modules/checkbox-and-radio.less:
  Remove hover state for checkbox icons for iOS usability
  Change a couple tabs to 2-spaces
- Other less changes:
  Escape all relative paths so that lessc compiles with correct relative path

Fixes Issue #70 (possibly) and issue #76
Merge pull request #77 from thcipriani/bug/ios-checkbox-usability

Remove Checkbox Hover, Escape Less Relative Path