Merge pull request #197 from jrrideout/death-march

Add R biom package link to docs
Fix --float-fields ref in docs
Fix formatting issues with sparse backend docs
fixes #189
Merge pull request #198 from gregcaporaso/death-march

added doc on enabling tab completion with the driver script
Merge branch 'death-march' of github.com:biom-format/biom-format into death-march
Update tab completion instructions