Upgraded all dependencies. This includes upgrading to PostCSS 6. When updating eslintrc I tried to keep same rules with new eslint, and added es6 support -- but I did this pretty quick so... I think it is good though.
Removed "postcss-message-helpers" dependency since it is no longer needed.
Merged two js file into one to help simplify the changes
Added option "functionName" that can be used to change the name to something other than "strip"
Updated the version of this package to 2.0.0 since updating to PostCSS is a breaking change.
Added postcss-reporter as a dev dependency and using in unit test to report PostCSS warnings nicely. Useful to see when working through a failing unit test.
Made it so the plugin leaves original value in place instead of printing out NaN. Warning is printed when this happens.
Added some more unit tests to cover new functionality and a few other minor things