Update gems to remove hash with indifferent access

Updated some gems and removed hash with indifferent access which was
still sitting idle in the repository class.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add index to make statistic compilation scalable

The statistic compilation for the resources did not scale. There was too
much data for sort() in MongoDB. Hence, I have added the appropriate
index.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>