API fixed, wrapper methods for the bit that does the work added
Added unit tests for convert_to_string
Implemented _internal_write, added one more unit test
Tidied up comments
Added hack to avoid bug in python < 2.7: http://bugs.python.org/issue2263
Added the write functions to the USAGE example in README.md
Labeled code block in README.md as python to enable syntax highlighting by github
Cleaned up 3 comments in converters.py
Removed test_very_large_ndarray, because it sometimes causes memory errors when it creates a 4GB numpy array.
Added unit test for convert_to_file, using a BytesIO stream to mimic a file
Merge pull request #3 from andres-s/write_functions

Write functions
Update README.md
Package prepared to version with write functions.