hmac only works with `str` type in Python 2

See also http://bugs.python.org/issue5285
Prepare v1.2.244.dev
Added url_title parameter to pushover plugin
Merge pull request #407 from calvin/develop

Fixes for send_email plugin, hmac only works with `str` type in Python 2
Merge pull request #408 from Bop4yN/develop

Added url_title parameter to PushOver plugin. Use 'urltitle' to setup your own title for url.
Stop using task.session in discover plugin. refs #2825
v1.2.244