Removed `bsSize` and `bsStyle` modifier mixins
Merge pull request #34 from pieterv/remove-bs-mixins

Removed `bsSize` and `bsStyle` modifier mixins
Add transitions to `Panel`
Tweaks to `Modal` docs
Add docs for Panels
Renames `initialActiveKey` to `defaultActiveKey`
Add hopepage masthead with logo to docs
Add docs for `ProgressBar`
Change `text` prop to `label` and add `srOnly` prop
Add gh-pages link to readme + tweak authors