compare_alpha_diversity now relies on skbio

updated the compare_alpha_diversity library so that it now utilizes skbio.math.stats.test rather than the qiime.pycogent_backports.test. also made a documentation change and a change to parser to ensure the tests could run.
Makes compare_taxa_summaries.py depend on skbio

Simplicity of this commit belies how difficult it was to figure out this problem. Referenced in commit b8701c4cf4497a9470defc4320125847ab074996 on the skbio PR.
group.py now depends on skbio
make_otu_network.py now uses skbio
Updates of otu_significance.py for skbio

Everything works as expected except the Mann-Whitney-U test because of the error I identified.
otu_significance.py now depends on skbio

moved everything required for otu_significance.py to skbio. needed to make substantial changes to the mann whitney u tests because the way ties are handled appears to be different in scipy. i checked the values with R, but R and scipy do not agree: eg. http://stackoverflow.com/questions/12797658/pythons-scipy-stats-ranksums-vs-rs-wilcox-test
stats.py now uses skbio

Had to update mc_t_two_sample in skbio to return a nan rather than a None but otherwise no other changes other than imports were required.
Final updates prior to removal of backports

This commit removes dependance for several scripts, tests, and libraries so that skbio should be the only thing required. Verified with ```grep -nr 'from qiime.pycogent_backports.test' .```. Only the tests will tell however.
Merge branch 'master' into test_port
Commit to remove backports test

This commit removes qiime/pycogent_backports/test.py and qiime/tests/test_pycogent_backports/test_test.py.
Merge branch 'master' into test_port
Renamed to accomodate skbio changes
Removed a pycogent import

Missed this import. Removed and tested.
Merge branch 'master' into test_port
Merge branch 'master' into test_port
Resolved mwu bootstrap failure

Moving to scipy's MWU test caused some interesting failures from tie corrections that failed.
Move and update

This commit moves the skbio.math.stats.test functions and associated tests into qiime.stats.
It also updates them to import from numpy rather than use np.function.
QIIME depends on qiime.stats

This commit makes qiime depend on qiime.stats rather than skbio.
Resolves none/nan problem

This commit should resolve the test failures.
Resolves some incorrect documentation

Resolves incorrect documentation and some commented out imports.