Added more tests for worksheet formatting.
Added initial support for worksheet protection.

Issue #4.
Added comparison tests for worksheet protect() method.
TravisCI config file.
TravisCI config file.
TravisCI config file.
TravisCI config file.
Added password hashing to worksheet:protect().
Added docs for worksheet protect() method.
Prep for release 0.0.6
Merge pull request #5 from jmcnamara/master

Release 0.0.6