This bumps the extension requirement to 1.2.0. Composer allows dev versions with the "^" operator, so this will accept 1.2.0alpha3, which introduces a "collation" option for Query and BulkWrite methods.

GridFS streams do not yet support seeking (PHPLIB-213), and HHVM requires a stream_seek() implementation in order to pass a non-negative offset to stream_get_contents().

HHVM does not support comparing ObjectIDs with the equality operator (i.e. `==`). For documents, which may contain arbitrary BSON types, converting to JSON is the easiest solution. The documents will then be compared as extended JSON and produce a readable diff on error.