Use the customer_id for projects index if it is provided.

Fixes #14
Added helper function to return an ordered project list.

Project list has entries for :active, :inactive, and :closed.
Changed ordered_projects to default with empty lists for categories
Projects are now listed in order of importance.

The three categories, listed in order:
* active (new, in progress)
* inactive (waiting on customer, on hold)
* closed (cancelled, completed)

Closes #34
Merge pull request #41 from matthew-parlette/simple_project_filtering

Simple project filtering