TST: Add interface to run tests from python

Tests can now be run using:

>>> import skbio
>>> skbio.test()
ENH: Add test suites and test data to package_data

Before configuring the setup function for skbio, gather the paths for
all the tests and test data.
TST: Remove deprecation warnings

The usage of self.failIf and self.failUnless is soon to be deprecated so
noesetests was raising a few warnings about it.
TST: Add support for NumPy's in-session testing

Tests can now be executed from within a(n) (I)Python session by calling
something like:

>>> import skbio
>>> skbio.test()
.......... .....
XXX Tests OK
>>> skbio.parse.sequences.test()
........ .......

This is as suggested by NumPy's guidelines, see [1] for more information
about this  document for more information about the configuration.

Notes:

The only odd thing is that if we add the few configuration lines as
suggested by Numpy's documentation, then we end up with an error like
this:

>>> import skbio
>>> skbio.test()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/yoshikivazquezbaeza/git_sw/scikit-bio/skbio/__init__.py", line 54, in test
    return Tester().test(level, verbosity)
  File "/Users/yoshikivazquezbaeza/.virtualenvs/skbio/lib/python2.7/site-packages/numpy/testing/nosetester.py", line 146, in __init__
    raise AssertionError
AssertionError
>>>

That's the reason why we are not doing it as the documentation suggests.

[1] https://github.com/numpy/numpy/blob/master/doc/TESTS.rst.txt
Merge branch 'master' of git://github.com/biocore/scikit-bio into numpy-testing

Conflicts:
	skbio/core/__init__.py
	skbio/draw/__init__.py
	skbio/format/__init__.py
	skbio/maths/__init__.py
	skbio/maths/stats/__init__.py
	skbio/parse/__init__.py
	skbio/util/__init__.py
MAINT: Remove retrieval of tests and data …

@Jorge-C noted that there's no need to include the filenames of the
tests in the package_data parameter as there's an __init__.py file being
included in each test suite already. As for the test data, given that
the only module that relies on test data is ordination, it is better to
hard-code the path instead of retrieving the information module per
moduel.

Fixes #247
STY: Remove new line at the end of __init__.py
DOC: Add note about testing to Contributing.md

Thanks @ElBrogrammer for the suggestion.
Merge branch 'master' of git://github.com/biocore/scikit-bio into numpy-testing
DOC: Add suggestions made by @gregcaporaso
Merge pull request #251 from ElDeveloper/numpy-testing

Numpy testing