Updated README file

Updated the README file:
* Changed to reStructuredText markup (using the `.rst` extension) instead of `.md` Mark Down; allowing merged cells in the table headers of the Pin Layout table.
* Added pin layout for the Arduino Nano v3 as requested in #32.
* Added a Hardware and a Protocols section, based on information provided in `.h` file.
* Added a History section, based on information found in the library as well as the examples.