Merge pull request #38 from azul/feature/meainingful_couch_error

catch Errno's and RestClient errors and throw a more meaningful error
Merge pull request #39 from azul/feature/keep-session-secret

fetch secret token for signing cookies from config
added vim tempfiles to gitignore
initial token model and unit test
let's use safe ids instead of the default couch ones

Couch uses partly random partly sequential ids by default. We could
change that in couch config to be all random. But this is probably more
safe.
return token on successful login via api