Check does not check the entire repository

[SiddharthManthan]

This is continuation of #75.

Problem

• Currently check randomly selects a part of repository.
• This does not guarantee the all the data will be check after sufficient runs. (Source)

Solution

• Implement --read-data-subset=n/t (Documentation).
• It will check all the data after sufficient runs.

I have filed it as bug report because the UI currently does not mention that all data is not checked. There should be a warning or proper check support should be implemented.