Merge pull request #6 from gaillard/master

Run multiple mongo db versions and extensions in the travis build.
Update predis to 1.0.

The [release notes](https://github.com/nrk/predis/releases/tag/v1.0.0)
are pretty clear about BC breaks and none of them appear to affect our
usage of the client here or elsewhere.
Merge pull request #7 from nubs/master

Update predis to 1.0.
Update composer.
Merge pull request #8 from nubs/master

Update composer.
Use php 5.4 array syntax.