Repository type support (POM etc.)

[hantuzun]

I'm unable to try com.github.fommil.netlib/all with lein-try. Adding POM type support could be a nice improvement.

[xsc]

Note: This happens because lein-try inserts

[com.github.fommil.netlib/all "RELEASE"]

into the :dependencies of a project, but should be inserting

[com.github.fommil.netlib/all "RELEASE" :extension "pom"]

in this case. Not sure how to handle that on a CLI level, though.