Adding the possibility of creating stderr and stddev plots on the same run for run_alpha_rarefaction
x_values are now scaled into range.

Still need to do some more testing.
Adding test for test_run_alpha_rarefaction_stderr_and_stddev
Raising the timeout to 180
Added auto distribution width calculation.

Removed --group_spacing from make_distance_comparison_plots.py. Still need to add/fix unit tests.
Updated unit tests.
Cleaned up code a bit and made it more efficient.
Updated ChangeLog.
Merge pull request #846 from jrrideout/mdcp_fix

Minor fixes to make_distance_comparison_plots.py
Merge pull request #841 from antgonza/alpha_workflow_two_plots

Adding plot_stderr_and_stddev in run_alpha_rarefaction
Finalized unit tests for usearch6.1
Merge branch 'master' into issue-833

Conflicts:
	ChangeLog.md
Merge branch 'pick_otus_usearch_rev' of git://github.com/walterst/qiime into issue-833
fixed a couple of buggy tests