scope global variables under 'rupture'
base font size fix for @declandewet
Merge pull request #18 from jenius/scoped-globals

Scope global variables under 'rupture'
0.2.0
Refactor anti-overlap feature and merge in scoped variables

Changes:
- Merges with the scoped variables changes.
- `rupture.anti-overlap` variable now accepts booleans or single values, and can covert
  between pixel and em values based on rupture.base-font-size.
- `enable-anti-overlap` variable removed.
- `force-anti-overlap` argument renamed to `anti-overlap`, and now accepts the same
  values as `rupture.anti-overlap`.
- Fixes a bug / typo in the anti-overlap test.
- Update readme.