fix indentation
move STOMP frame marshalling to STOMPFrame

add description methods
add test with JSON payload
API refactoring + error handler

rename connectWithLogin:passcode:completion:
    to connectWithLogin:passcode:onConnection:
and all associated methods

rename subscribeTo:handler:
   to subscribeTo:onMessage:
and all associated methods

add connection method taking a ErrorHandler in case of error coming from
the server
update code snippet
Refactor API

map the API convention on NSURLSession
add heart-beat:0,0 to the CONNECT frame
Merge pull request #1 from jmesnil/master

API refactoring