Removed text/plain from MIME types in gedit/scala.lang.

text/plain shouldn't appear in this file, since that causes
gedit to apply Scala highlighting to plain text files.
I also updated the install path in the comment at the top of the
file.
Merge pull request #82 from adam-yorba/master

please pull: updated syntax highlighting file for gedit
Merge pull request #83 from adriaanm/release-simplify

Simplify finding the distribution to release.
Merge branch '2.10.x'