typos, timings, removed gg download
addressing @gregcaporaso's comments
added mixed wget/curl command
Merge branch 'tutorial_updates' of github.com:wasade/qiime into tutorial-updates

Conflicts:
	examples/ipynb/illumina_overview_tutorial.ipynb
MAINT: more text clean-ups and updated to work out of the box with pip-installed qiime
removed statement about runtime

for pick_open_reference_otus.py. this goes much faster now without the pre-filter.
MAINT: misc fixes based on comments from @jairideout
Merge pull request #1697 from gregcaporaso/tutorial-updates

overview tutorial updates