when tern is installed, don't setup eclim's js completion

refs #244
update temp file cleanup use project.getFile directly

using ProjectUtils.getFile would trigger refreshes which aren't
necessary when we are about to delete the file.
RubyProjectManager.refresh(IProject, IFile): ignore IllegalArgumentExceptions

if the project is mixing more than one nature and a ProjectUtils.getFile
call is made on say a js file outside of any of the ruby src dirs, then
the subsiquent call to the ruby project manager would raise an
exception. For the sake of refresh, we'll ignore those exceptions.

refs #244