Add a test runner.

* Build the extension against ØMQ v2.2.0
* Run the tests, ensuring that the exit code is returned
Add Travis CI build configuration.
Install uuid-dev before running the test runner.
Build before testing...
"Manually install" the zmq extension.

Currently, very nearly all tests are skipped during the Travis CI
(see https://travis-ci.org/phuedx/php-zmq/jobs/11650067 and
https://travis-ci.org/phuedx/php-zmq/jobs/11650068). The majority of
tests are skipped because the zmq extension hasn't been loaded. Since
manually installing the runkit extension during the Travis CI build for
phuedx/pinkerton works, try manually installing the zmq extension here.
Don't check for memory leaks while running the tests.
Build against ØMQ versions 2.2.0 and 3.x.

The complete list of ØMQ versions is:

* 2.2.0
* 3.1.0
* 3.2.0
* 3.2.1
* 3.2.2
* 3.2.3
* 3.2.4
Build against ØMQ version v4.0.0.
Merge pull request #100 from phuedx/develop

Build php-zmq on Travis CI