FO-7 Check valid url address

Check if a url address is valid. Create a single regular expressions with all the rules you have learned in order to accept data into following format.

1.http://www.lettersornumbershere.extensionhere

2.https://wwww.againnumbersorletters.extensionhere

The rules are simple, the first part must be literally either http or https. 

Follows literally the '://www.' part. This is like a constant. It must be there exactly as it is.

After the literal dot follows an unknown series (lets put it between 2 and 50) characters that could be either letters or digits, followed by a literal dot . at the end of it.

After the dot, follows the last part which could contain only letters (min 2 and max 4 characters).