Added more bitcoin tests
video_device default should be string
Added util test file
Comment on wallet classes. Use address_is_old to check if address is beyond gap limit
Added mnemonic to seed tests
Merging master to add-more-test to fix travis

This will make travis tests work on this branch as well.
Merge pull request #732 from chrisglass/fix-travis

Fix travis
Merge pull request #733 from chrisglass/add-more-tests

Add more tests