ENH: Add iter_regex and find_features

Fixes #612. Adds iter_regex to skbio._sequence.BiologicalSequence and
find_features to skbio._sequence.NucleotideSequence. Supported features are
currently purine_run and pyrimidine run, but more can be added by specifying
additional regular expressions.
Simplify the regex considerably

Not quite sure what I was thinking with that one
Add option to allow gaps
Creates power analysis code
Fixes spelling issue
Fixes formatting issues

Fixes pep8 and flake8 format issues
Also comments out alignment in the __init__ file since this was causing
the data to error.
Fixes import random error
Fixes more imports because pep8
Fixed spacing issues
removes unnecessary imports
Adds alignment back in to __init__
Switches from python to numpy

Substitutes numpy.random.choice from python’s random.sample. This will
coerce data to be numpy vectors.

It should also hopefully fix the Python 3 compatibility issues.

Also moves the test functions to a more appropriate folder.
Increases tolerance on confidence bound
Move feature types into class hierarchy

Also add some additional tests
Handles numpy compliace and testing

Continues the switch from python to numpy, including setting a random
numpy seed which should hopefully work with python 2 and python 3.
Moves the random seed into setup

This should hopefully fix randomization issues between the Nose module
and the Python test module.
Adds a function for subsampling

Introduces subsampling to get even sized groups for comparison with a
p-value similar to the p-value of all the data.
Adds alignment to _init__
Merge branch 'master' of https://github.com/biocore/scikit-bio into Power
Updates branch with upstream branch