Split docs up into OS-specific install instructions. Fixed some taxonomy doc errors. Merged the OS X and Windows taxonomy instructions.
Fix links in README.
Fix links in README, again.
Fix links in Linux & Windows to taxonomy instructions.
Remove duplicate info in taxonomy doc.
Merge pull request #247 from terrycojones/taxonomy-docs-errs-246

Taxonomy doc corrections

Fixes #246
Add --invert flag to filter-fasta-by-taxonomy.py instead of --rejects to make it more flexible in use as a filter.
Merge branch 'master' into filter-fasta-by-taxonomy-248
Improved taxonomy docs.