Minor improvements to the server roles model

- Some bugfixes where we should've been using .server_roles for roles selecting/deselection
- Added a property for inspecting the current reported server roles
- Stripped the 'server_roles_' prefix off of role names, that's unique to this page and not part of the actual role names
Merge pull request #73 from seandst/add-roles-fixture

Minor improvements to the server roles model
Added Chargeback Automation Pages

updated_chargeback_page

fixed the selects to use page.select_dropdown

made my if statements default to none and made the variables lowercase

Updated the Chargeback Page

Chargeback Test
fixes #75: Speed up tree traversal over leaf nodes

For some (unknown) reason, when trying to find a node by name/regex/substring in a Tree
or Tree subclass, the following-sibling::* XPath was being really slow (exactly 10 seconds
every time a leaf node was being examined in the "while queue" loop). I moved the XPath
following-sibling behavior out of the browser and into python; it seems much faster now.

While I was in there, I hit Tree.find_node_by_regexp with the DRY stick by seeding the queue with self instead of self.children.
tweak locators to work for both 5.1 and 5.2
Merge pull request #76 from seandst/speed-up-tree-leaf-nodes

fixes #75: Speed up tree traversal over leaf nodes
Merge pull request #78 from dajohnso/locator_tweaks

tweak locators to work for both 5.1 and 5.2
Merge pull request #72 from jwadkins/chargeback

Chargeback Automation