Created as ruby gem, added instructions, better output file configuration, error handling and help commands

@dreeve and @amgando if you guys have a chance to look at this it would be awesome to get your feedback on the code in this staging branch (should be functional and bug-free, -ish). We expanded on our snippet group project to make it a little more fully featured and useable as a learning tool among the cohort. But we're not sure what a gem is really supposed to look like, so any feedback on design or functionality would be great, as well as your perspective as developers on what could make this more useful/useable. Thanks in advance for any feedback.

All - updated the readme file with a animated gif showing the functionality, also added some better output messages on terminal. You should be able to install from the source directory with `rake install`, the run `snip <filename/directory>` anywhere. Test files can be reset with `rake seed` to make it less manual to change those test files after each run. File output directory/filename can be configured with `snip -f <filename>`, e.g. '~/desktop/my_snips.rb'.