Merge pull request #1 from datasift/develop

Develop
Merge branch 'release/2.0.0'
sanity check for built against version
Merge branch 'develop' of github.com:benjamg/zmqpp into develop
tidying of tests and switch to zmq_msg_send for non 3.0
fixed std:move issue with sockets not correctly initialising data
don't keep ownership on error
added 2.x socket options, broke message send against 2.x
everything but get socket options working
test other than load test run correctly
Merge branch 'feature/0mq2.2-support' into develop
fix tests for 3.0
support for changes in option types in 3.1 (and 3.2)
Merge pull request #2 from datasift/develop

Develop
fixed load tests to actually work again under 3.2
Merge pull request #3 from datasift/develop

fixed load tests to actually work again under 3.2
updating version to 2.1.0
Merge branch 'release/2.1.0'
Merge branch 'release/2.1.0' into develop
Update develop