conn: support session specific message timeout
Merge pull request #58 from mreiferson/msg_timeout_58

configure session-specific msg_timeout
AddHandler refactoring

* remove unneeded check for adding more handlers
* rename Set->AddHandler
* check for handlers on lookupd connect
* panic on already connected to nsqd/nsqlookupd
Merge pull request #48 from jehiah/concurrent_handlers_48

separate handlers for concurrent handlers
changelog/migration guide
Merge pull request #57 from mreiferson/changelog_57

0.3.7 to 1.0.0-alpha migration docs