Don't check for metaFile if non-Apex extension

make sure we got back at a metadata type for the extension before
checking to see if we should include the metadata xml file.

Fixes https://github.com/joeferraro/MavensMate-SublimeText/issues/155
Merge pull request #37 from doublesharp/patch-compile-non-apex-extension

Don't check for metaFile if non-Apex extension