Copy in tests from Manfred Moitzi's xlwt3
Add sample files needed for tests
Fix tests to pass on Python 2 and unmodified xlwt
Relicense tests to BSD

This was agreed to by Manfred Moitzi, the author of these files.
https://bitbucket.org/mozman/xlwt3/commits/cc8ee488d684e3ef91fd5dc3da460db0261eeb7a#chg-tests/test_biff_records.py
Add travis config
Merge pull request #42 from takluyver/manfred-tests

Tests from xlwt3
Add ability to insert bitmap images from in-memory copies.
Missing 'return' from _process_bitmap.
Add regression tests for insert_bitmap and insert_bitmap_data functions.
Fix merge conflict.