Issue 71 - insert/update/replace/delete

I've only updated the JavaScript files (and not the index).

@coffeemug could you take a look at it? I'll copy paste to other languages when there won't be any error left.


Also from writing the docs, I ran into a few issues:
- We cannot do a upsert that behave like a replace -- See https://github.com/rethinkdb/rethinkdb/issues/1570
- The `nonAtomic` flag doesn't exist for `replace`. Is that expected?
I am also not convinced that we need this flag.


I didn't write on how to handle errors with write operations. If we don't plan to address https://github.com/rethinkdb/rethinkdb/issues/899 in the near future, I'll add some recipes in the cookbook or maybe write something about best practices (that would include how to use connections, cursors etc.)

Related issue: #71