Tweaks based on comments by @nviennot

types at the command line are lowercase
':object' is now the dummy type
Generated models now include NoBrainer::Document::Timestamps by default
index declarations are inline with fields
The generator wasn't accepted, so the app creation section is more explicit
Rewrote an awkward sentence
Minor tweaks to rails tutorial
Merge pull request #427 from rethinkdb/josh/nobrainer_updates

Tweaks to rails tutorial based on comments by @nviennot
s/:index => :name/:index => true/
Corrected `Accept` header documentation

Fixed docs based on rethinkdb/rethinkdb#2695
Merge pull request #429 from rethinkdb/josh/nobrainer_updates

s/:index => :name/:index => true/
Added new illustrations

map-reduce illustration
secondary-indexes illustration (ruby/python/js)
data-modeling illustration
table-join illustration