Added content on Mongodb
Added content on Mongodb

Regarding Mongodb pro's con's, indexes, shards, replica and such
reykjavik-university/2014-T-514-VEFT,reykjavik-university/2014-T-514-VEFT,reykjavik-university/2014-T-514-VEFT,reykjavik-university/2014-T-514-VEFT