Raspberry pi support

Mockgoose doesn't run on the raspberry pi: 

unsupported architecture, ia32 and x64 are the only valid options

Note that MongoDB is version 3.x and not 2.4 or 2.6 that is shipped by default in raspbian. Even though MongoDB is 32 bit, it would be nice to be able to run headless test on the pi.

It does run on x86 build of raspbian stretch with MongoDB 3.x