test: import cleanup & nosetests intro

While investigating how to deliver a clear user/developer interface for MONK's
unittest suite, I found that `nosetests` is a rather powerful tool for testing.
As far as I understand it is a framework/tooling around Python's unittest
library adding more features.

Those features include:
 - automatic test discovery, no more need for test suites (but still possible)
 - simpler test methods without TestCase overhead and without removing any
   feature
 - decorators for Exception testing -> simpler code
 - plugins for coverage
 - plugins for various xml output

That's why nosetests seems to be the standard tool for unit testing in the
Python community.

Making the decision to use nosetests and the need to change the unittests to
comply with the new virtualenv-install-import policy makes a rewrite of the
existing unit tests rather attractive. This commit starts that approach,
deleting all the old school unit tests (which can be retrieved later on if
necessary anyway).

The first test will be about serial_conn, because there is the next development
focus for MONK. It imports monk_tf and creates a SerialConn object in a very
code-effective nosetest.

Then setup.cfg and setup.py were adapted. Now it is possible to simply call the
following line and let setuptools and nosetests do the rest:

    $ python setup.py nosetests

You can try it yourself with the following lines. But first make sure that you
have "Python2.7-dev" and "libssh-2-1-dev" installed on your system. Both are
not Python requirements, so MONK can't handle them itself.

Here's the example for you to follow:

    # checkout a fresh MONK
    $ mkdir fresh
    $ cd fresh
    $ git clone git@github.com:DFE/MONK
    $ cd MONK
    # checkout this commit
    $ git checkout <this commit>
    # create a virtual conf to not play around with your system configuration
    $ virtualenv .
    $ source bin/activate
    # now let the tools do their jobs
    (MONK)$ python setup.py nosetests
    <installing requirements>
    <installing monk_tf>
    check if creating a SerialConn object works.. ok
    <coverage statistics>
    <test results>

    OK

With using `$ python setup.py develop` it's also possible to change your code
and test suite while also being able to unit test it with `$ python setup.py
nosetests` on the fly. Google for `setuptools develop` or ask me, if you want
to know more about that.

Last but not least this commit changes the place of the monk_tf folder again.
The reason is, that all the tools' default behaviour is to expect the structure
without the src/ folder. Before we decided that the src/ folder would be a
better choice, because then potential additional packages might be structured
in a more readable fashion with monk_tf. Because different tools are
interacting now and each has the same default expectation it seems more
logical to follow that expectation in the future. That's why this commit
changes the structure instead of configuring all the tools to our structure.

See Github Issue #34.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
.travis.yml: Update for simpler unittesting

Because the interface for testing and installing did once more got closer to
the standard, there is already a payoff in the travis-ci configuration, were
now less lines of code are needed.

In the new configuration the setuptools standard interface is used for
installation as well as testing. The only requirements necessary for
installation left are python2.7-dev and libssh2-1-dev, which are C-header
dependencies needed for pylibssh2 to build. As far as I see there is not much
we can do about those requirements for now.

See Issue #34.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>