Using the bin path at root of pwd

The compile script is run with the root of the git repo of the project
being pushed as the working directory.

$BIN_DIR is pointing to the bin directory of the buildpack which is not
where you would want to put the pre and post compile hooks.

Changing back to the old convention of looking for the hooks from the
bin directory at the root of the project.
Merge pull request #86 from manojlds/master

Fixing the compile hook scripts paths