Updated the README based on all the recent changes

This gets the README lined up with all the changes to DatTCP's
interface and inner workings. Now the README will correctly tell
how to use DatTCP.
some README, LICENSE, and gemspec rewordings and updates

Just trying to improve the readability a bit.  Added Installation
and Contributing sections to the README.
Merge pull request #13 from redding/kr-readme

some README, LICENSE, and gemspec rewordings and updates
Merge pull request #11 from redding/jcr-readme-updates

Updated the README based on all the recent changes