Makes between followed by order_by not drop the between.

All existing tests pass. Now it's time to write tests for the new
behavior.
Adds tests which fail for order_by and between.
Adds more failing tests.
Merge branch 'order_by_between_test' into order_by_between
Makes for chained order_by and between pass.
Add an example with r.desc when using an index
Make examples consitent accross languages + Wrapping the js example in quotes so pyyaml doesn't complain
Use : for ruby + wrap js example in quotes. ROTS by @jdoliner
Add a failing test for get_all and order_by.
python driver code ported to python3
Add not_() to python driver

Pull request reviewed by @atnnn
Closes #1329
Closes #1360
Make order_by not drop get_all.

Also adds tests which test this.
re-adds protobuf_implementation to JS driver
Merge branch 'next' of github.com:rethinkdb/rethinkdb into next
Pass rcheckable_t *s rather than backtraces.
Fix a bug with referencing sindex_id rather than _sindex_id.

Also renamed _sindex_id to make this mistake less likely.
Redo an error message.
Improve an error message to reference indexes.
Add missing "err." in the js driver

Review 879 by @neumino
Add tests for unindexed order_by followed by indexed.