(add some module-level docstrings)

Ignore-this: 476077218168abc32f21fe9f5d5c00d9

darcs-hash:20130920205424-3a4db-8b76b42bd6b4e2188ce34fec9db4eb0bfcc4eba3
(test_bandmat - minor improvement)

Ignore-this: dda91b0365a34d682661ce404c23e83d

darcs-hash:20130920210722-3a4db-aa6d1ad321fc3f73b15d5e5613507bd5fd269c44
add a well-tested module for banded operations on full matrices

Ignore-this: af3b71dfcf455744689bf9087ff1806f

darcs-hash:20130920233014-3a4db-2a668d73b5d179ad35e7de1787bff6c0cc611323
add requirements file

Ignore-this: 2b7a15874792a150fe22fff591070925

darcs-hash:20130921012054-3a4db-d38f79f9d801fb1bf2c95492a5bce16843270fa8
add a travis CI file

Ignore-this: 45a32a3c6c2c73062545a60e9ce6bad3

darcs-hash:20130921012526-3a4db-a1d984f26eab88dea98bb6752312d2fada63268b