REL: Version 0.3.3 with working conda build + TD04AD fixes

This release of the Slycot library contains a working conda build process plus fixes to the TD04AD function (including fixes issues with edge cases). The README.rst file has also been updated to reflect the current build process. See PR #26, PR #27 (based on PR #25), and PR #28 for details.

Note: the current Travis CI build process intermittently fails due to issues in python-control (to be corrected in the next release of that package).