Merge pull request TEOS-10#50 from ocefpaf/fix_travis-ci

Fix travis-ci and add versioned docs.

Merge pull request TEOS-10#44 from efiring/salinometer

Add new salinometer functions from GSW-C.

use oldest/newest numpy possible+don't build wheel (TEOS-10#34)

use versioneer to handle version number (TEOS-10#25)

Fix Development Status classifier (TEOS-10#15)

* Fix Development Status classifier

Merge pull request TEOS-10#11 from ocefpaf/bump_version

Bump version to 3.1.0