sqlite3 implementation for raspberry pi instead of MongoDB

[drascom]

hi Georgios , thank you for this great work and well organised codebase.
I noticed we cannot install mongoDB to raspberry pi devices (raspian debian based but there is no support foor arm based devices at mongo side)
it is possibble to install ubundu on raspberry but it consumes lots of process power.
i'm thinking to implement sqlite3 instead of mongoDB this weekend.
i'll create pull request than you can check and you can create another branch for arm based devices if you like.

[jameswynn]

This was a great idea. I just submitted a PR for this: #125