[rand]: Check user input is valid

* Check if user input is valid and print a corresponding message if it's
not
[admin]: Check if user input is valid

* Check if user input in .me and .msg is valid
[calc]: Check if user submitted input

* Verify that the user submitted input to be evaluated
Merge pull request #464 from Erethon/feature-fix-modules

[rand,admin,calc] Check if user input is valid