DOC: Add note about py3k

The README.rst file was listing 2.7 as the python version needed, which
is misleading as skbio supports 2.7 and 3.4.
DOC: Make documented version more inclusive

Thanks @Jorge-C
Merge pull request #388 from ElDeveloper/3.x

DOC: Add note about py3k
Skip another stochastically-failing test

See #386.
Merge pull request #391 from ElBrogrammer/skip-stochastic-failures-2

Skip another stochastically-failing test