Bourbon Compatibility

converting color stops back to percentages for bourbon compatibility

SassConf 2013 Update

• Now requires Compass 0.13 or higher (or Bourbon 3.1.8)
• $gradient-colors & $gradient-stops have been combined into 1 multi-dimensional list
• Default values for function are now !default flagged, so they can be adjusted on a per-project basis
• Updated README to reflect code changes

Original Release for CSSConf

Merge pull request #1 from steveax/fix-typos

Fix typos in README ('gradent' -> 'gradient')