Fixed script mime-type bug

Fixed the demo at http://learnboost.github.io/antiscroll/
which was not working in (atleast) Chrome 27 due to this error:

`Refused to execute script from 'https://raw.github.com/LearnBoost/antiscroll/master/antiscroll.js' because its MIME type ('text/plain') is not executable, and strict MIME type checking is enabled. `