Small changes and bug fixes

- Added `.csscomb.json` to cleanup CSS
- Cleaned up CSS with CSSComb
- Added `bootstrap.php` with new list group walker class
- Pulled options from `steel.php` into new `options.php`
- Deleted `leftovers.php`
- Fixed `run.js` to avoid conflict with new Audio List feature in WordPress 3.9
- Fixed columns shortcode to reflect Bootstrap integration
- Added transitions to Slides module
- Function `steel_version` deprecated and replaced with `$steel_ver`
- `$bs_ver` added
- `module` tags removed, `package` tags updated
- New Navigation Menu widget