allow plugins
improved alpha channel handling for math ops
fix for less.js 1689
color-blending-with-transparency
Add ModifyVars() and serializeVars()
jshint: eval option
Experimental support for mixins with interpolated selectors.
prevent undefined index
implementation of mixin guard `default` function
add Less_Tree_DefaultFunc
remove alpha from contrast calc
fix issue with urls in mixins
property name interpolation
only build master branch on travis
fix issue with unquoted urls in mixins having their context evaluated
fixed merging of interleaved properties
clamped rgba format color output
 `default` function: added error when used with css-guards
data-uri function used single quote, switched to "
fixed using starting index for parser nodes for accurate source maps