Update README.md

add troubleshooting section

For now, just include how to deal with the too many files open error.
I'm pretty sure there's another error message I should include that
I've missed, but I can't track it down at the moment.
Merge pull request #31 from kbaribeau/master

Add docs around "too many open files" error
Merge remote-tracking branch 'origin/master' into proxy-server
Added an API proxy option that receives all 
messages not satisfied immediately by a static
asset in /generated.