Stop validating a file when the failures reach a certain threshold

[haritha-ravi]

I intend to add an enhancement to vladiate which would optionally stop validating a file when the failures reach a certain threshold.

To add more context here, this is an idea to overcome an issue we are facing. We do not want to further process a file if vladiate returns a fail_count more than 10%. But currently there is no feature in vladiate to stop validating a file earlier. So we have to validate rest of the even though we could stop early. This proves especially troublesome when validating really large CSV files.

I have created a PR to introduce this: #89