+ Update docs + Update .gitignore
+ Update docs
+ Update .gitignore

Signed-off-by: Aymeric Brisse <a462d6a602eb500679b027b39ff035d803cbe1e9@perfect-memory.com>
drobune/mongoid-multitenancy,PerfectMemory/mongoid-multitenancy,vladzloteanu/mongoid-multitenancy,hiroshi/mongoid-multitenancy