Automatically set PATH and LD_LIBRARY_PATH

this is inspired by https://github.com/shunjikonishi/heroku-buildpack-ffmpeg/blob/master/bin/compile
Merge pull request #10 from jigfox/patch-1

Automatically set PATH and LD_LIBRARY_PATH
revert pull request merge
Pointing to Bitbucket where PhantomJs downloads will be hosted henceforth. Upgrading to 1.9.7 from 1.9.2
curl does not follow HTTP redirects automatically, so adding the
-L option which is needed by bitbucket, as the download is from a CDN