Add v:throwpoint to catch in neobundle#config#source
Use 'silent! unsilent source' in on_source

"silent!" is required to ignore E122, E174 and E227, and "unsilent"
displays any messages.

Thanks to Ingo Karkat!
Merge pull request #342 from blueyed/revert-try-cache-with-source

Revert try cache with source