Add license and clean up readme & help command

Added MIT license file and notice in readme.
Cleaned up help text in readme and also in the help command a bit,
trying to make it a little more professional.
Update main file comments; Set to v1.0.0

Updated comments in keep_secret.rb to be clean and informative.
Set version to 1.0.0 (from 0.1.0)
Removed pry requirement.