Changed non-hash user defaults. Tightend tests.

Added managehome => true to defaults hash for new users passed in
as a string or as an array. This will cause puppet to create the
users home directory by default.

Shortened tests in stackable_base_spec.rb using loops! Yay! They
should run faster and be easier to read. Have fun.
Seperated user creation into it's own class.

For readability. Added comments and notes in spec tests.
Modified spec tests appropriately