Option to use SSL for PushoverHandler (enabled by default), and close connection after sending a message to PushOver.

Solves #146: When sending messages in rapid succession to pushover.net only the first one is sent.
The SSL option is needed when sending messages to users that are not the pushover.net app owner; pushover.net doesn't accept those messages over plain HTTP.
Make ChromePHPHandler and FirePHPHandler sendHeaders flag static so that when multiple instances of the handler class exist they will all respect the one-time check that determines whether the handler should append its logs to the response header
Fix permissions
Fix test suite
Update branch-alias
Enable initialization of zmqHandler with either a dsn string or a zmqsocket