Refactor & add unittests for almost all functionality, add tox for running tests on py27 and py35 (#17)

* Refactor & add unittests for almost all functionality, add tox for running tests on py27 and py35

This commit adds unit tests for current api functionality.
- currently no mocking, all tests are run on the device.
- the library is now compatible with python 2.7 and python 3.5, use tox for tests
- schema checks are done with voluptuous

refactoring:
- protocol is separated into its own file, smartplug adapted to receive protocol worker as parameter.
- cleaned up the initialization routine, initialization is done on use, not on creation of smartplug
- added model and features properties, identity kept for backwards compatibility
- no more storing of local variables outside _sys_info, paves a way to handle state changes sanely (without complete reinitialization)

* Fix CI warnings, remove unused leftover code

* Rename _initialize to _fetch_sysinfo, as that's what it does.

* examples.cli: fix identify call, prettyprint sysinfo, update readme which had false format for led setting

* Add tox-travis for automated testing.

.travis.yml

@@ -0,0 +1,9 @@
+sudo: false
+language: python
+python:
+  - "2.7"
+  - "3.4"
+  - "3.5"
+install: pip install tox-travis
+script: tox
+