Adding new flexible_attrs class attribute.

This will hold (in order) the attributes that can be used as object references
for easy lookups.
Adding Flexible object method (test).
flexible -> resolvable -- better name
Removing unnecessary whitespace.
Cleaning up our Account class.
Adding in tests around resolve_group helper for accounts.
Removing Account.resolvable_attrs.

This isn't being used since it's basically impossible to make things work this
way :()
Cleaning up Account._resolve_group.

It now provides an AMAZINGLY AWESOME interface for developers. You can get a
group in any way possible =)
Removing Group.resolvable_attrs.

Not used any longer.
Changing param name.
Cleaning up some logic.
Adding tests for our improve Group._resolve_account stuff.
Making Group._resolve_account work with custom search criteria =)
Cleaning up naming.
Spacing.
Spacing.
Adding new Account.add_groups() method.

This lets you add multiple groups to an account at the same time.
Adding Account.remove_groups helper.
Adding convenience methods for groups.
Merge branch 'develop' into simple-api

* develop:
  Updating changelog to include docs on password reset changes.
  Add optional account store for password reset
  Fixing UA.