Hubot script reloading without restart

Two new commands:
`hubot reload all scripts` will reload scripts in same fashion as a restart would do.
`hubot command count` tells how many commands Hubot is aware of. Good for testing if new scripts
where loaded / old ones removed.

Cleans up old listeners and help upon successfull reload.
Merge pull request #959 from spajus/script_reloading

Hubot script reloading without restart