Email users when their account is blocked

[saurav-codes]

I saw this in long term goal of this project & wanted to work on it.

[kencochrane]

Sounds good, thank you.

[saurav-codes]

@kencochrane I have created this PR #242
it's not the final yet. So i created this with initial changes. ( first make it work then optimize it ).
Here we are using a synchronous way of sending email to user ( i am getting the email by search user from username in DB )

please have a look and let me know what needs to change or improve. if everything looks good then i will proceed with adding readme and test for this change.