ENH: updated required skbio version
Merge pull request #279 from gregcaporaso/issue-278

ENH: updated required skbio version
ENH: Speed up the travis build

Installing Pandas and openpyxl with conda is much faster than resolving
the requirements using pip.
Merge pull request #280 from ElDeveloper/travis-speed-up

ENH: Speed up the travis build
Merge branch 'master' of git://github.com/biocore/emperor into issue_150