Added algorithm description and quality control headers to the main page
Initial commit of an algorithm description for PICRUSt covering the main workflow
Fixed links to citing_picrust
Initial commit of page detailing citation for PICRUSt, linking to the Werner labs page for citing QIIME, and also including citations for APE and COUNT since folks might want em
Initial commit- edits and some additional content needed
revisions to quality control discussion and addition of hyperlinks for the sections
Updated the quality control discussion
Edits to the algorithm description
Merge pull request #145 from zaneveld/doc_responsible_use

Documentation for 'How PICRUSt works' and Quality Control.  Addresses Issue #126.  Addresses Issue #127.