There is a 4.01-ism or two in the code
Update oasis to 0.4.4
Add support for more data types; Related cleanup/refactoring.

The (read|write)_int and (read|write)_float functions were removed
in favor of exposing the Band.read and Band.write functions directly.  This
keeps any data type conversion explicit.
Simplify transform functions; Add a bit of ocamldoc
Bump version