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.

Remove MongoDB 2.4 from the build matrix and use the latest stable driver by default.

Add explicit jobs to test MongoDB 2.4, driver 1.1.0 (oldest supported version), and the latest unstable driver version. Lastly, restrict PHP 5.4 and 5.5 to a single job each.