Adds a json term to the server.
Merge branch 'next' into json_term
Make json term accessible to the outside world.

Also make things work in the python driver.
Adds json term to javascript driver
Adds test for json term.
Adds docs for json term.
Return the json that failed to parse in the error.
Fixed btree corruption bug.
Do not leak processes during reql tests

Review 665 by @wmrowan
Closes #1055
Merge branch '986_btree_corruption_bug' into next
Merge branch 'next' of github.com:rethinkdb/rethinkdb into next
Use the correct ruby protobuf library on travis

Review 668 by @mlucy
Merge branch 'next' into merge_br
Merge branch 'next' into slava_docs