Added the environment variable HUBOT_SKYPE_ADAPTER_PYTHON for a custom location of the python executable

Signed-off-by: Philipp Beckmann <philippbeckmann@pabnet.de>
Update src/skype.coffee

Renamed env var to HUBOT_SKYPE_PYTHON to match existing vars
Don't react to own messages
Merge remote-tracking branch 'remotes/origin/Branch_envvar'
Changes for coming Hubot 3.0.0