fixed sourcemap to be included in third_maprty JS; added error handling for uproxypeerconnection
fixed support for empty strings
fixed independence data channels in chat2
a little layout cleanup
added printout for sent empty data
avoid chat demo from hiding bug on empty strings
fixes, w.r.t. review. fdom interface now includes errors
Merge pull request #59 from uProxy/iislucas-chat2-fixes

better error handling; data channel fixes; improved sample chat2 app