Updated to use more concise syntax

The program now encrypts using a map function. Because of the cycle
function python3 needs to be used. Also because python3 is used the
syntax of print statements was changed and raw_input was switched
to input.
Updated README.md
Now works on python2 and python3
Merge pull request #3 from cameronbwhite/master

Made code more concise and updated README with examples