Add tests for existing fill method (there weren't any)
Implemented optional stop_before argument to Bag.fill() which terminates the fill process.
Bump version in setup.py
Removed unused commits in test_fill.py
Use itertools.takewhile() function
Return false in __eq__ rather than assert.
Merge pull request #38 from scraperwiki/improve-fill-method

Implement a minimal stop_before argument to xypath.Bag.fill()