Bundling support

[nico-abram]

At least for windows, I think this might be pretty nice to have (Since for many people building and configuring can be a PITA). I mean something similar to what libsqlite3-sys does (Just compile the library in the build step)

If this is out of scope or wont-fix for some reason I apologize (A quick glance a the issue tracker did not show duplicates)

I'm not a diesel or pq-sys user myself but all the discussion in diesel's tracker made me think this might be desireable (To eventually maybe have a bundling feature in diesel and diesel cli)

[weiznich]

I've opened #46 for this. It is currently blocked on contributions from developers using macos and/or windows. If you use these systems consider helping to fix the remaining issues.

[weiznich]

Fixed by #46