Correction and extension

 - note that there are now more than one template

 - ignore that the default is now python services until this doc is
   completely overhauled

 - target the template to bash since all the examples are currently
   bash
Update the intro to writing hooks

 - use active voice
 - observe the all powerful tabula rasa charms present an author
 - introduce charm helpers
Merge pull request #164 from whitmo/master

Charm helpers entry point