Removed dependency on math module

All math.sqrt() etc replaced with numpy
Also added first test numpydoc docstring.
Adding comparative tests for numpy vs old methods

The idea here is to recreate all the current functions
with _np suffixes, e.g. tdev -> tdev_np, so as to compare
the output between new and old versions. Assuming that the new
versions perform better, eventually old code will be completely
replaced with the new code.

Initial tests see speedups in the range 50-200x, so very promising!
Added numpy versions of adev() and oadev()

New versions are signficantly faster -- as high as 400x for some settings.
Next on the hitlist is hdev_phase_calc() method, and the hadamard
deviation routines. totdev_phase() and mtie_phase() will be the main
sources of pain left.
Added hdev() and hdev_phase() numpy equivalents

Also added tests in np_tests.py. Next step is total deviation methods.
Added ohdev() and ohdev_phase() numpy equivalents
Added totdev() and totdev_phase() numpy equivalents

Tests against current pure python also added. Large speedup (>100x)
Added tierms() and tierms_phase() numpy versions

All that is left is the MTIE code, which is also the most daunting...
Added numpy three_corner_hat method
Moved numpy methods to new file
First full numpy-ified version of allantools.py

Finally figured out a numpy-ish way of computing MTIE. Unlike other
methods, the speedup is only modest (3x). Getting this to be faster
will require a quicker way to do the rolling window.

The new code passes the runtests.py test routines. The old pre-numpy
code has been moved to allantools_pure_python.py; I think this code
should stay as it's a good reference and shows the different ways
of thinking: loops vs. vectors. I've certainly learnt a lot by porting
it over to numpy!

Next on the agenda will be adding numpydoc docstrings for all the
methods, and then generating sphinx documentation. Then this will truly
be the most awesome toolkit out there for measuring time stability :)
Merge branch 'master' of git://github.com/telegraphic/allantools into telegraphic-master

Conflicts:
	allantools/allantools.py
	leda_avar.py
	tests/testutils.py
fix testutils.py
add a few comments