Refactored Cursor to provide a bookmark for current queryset

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Added query optimization to remove redundant where clauses.

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Added PEP8 exceptions

Signed-off-by: Kevin Stone <kevinastone@gmail.com>
Merge pull request #3 from kevinastone/simplification

Refactored Cursor to act as a bookmarking wrapper for querysets