Fix links to wiki in readme
Update README.md
Replace abbreviation
Merge pull request #10 from mmurdoch/master

Improvements to readme
Check ARDUINO_HOME before use on Windows

On Windows ARDUINO_HOME has a default of None but is used to determine
the AVR_HOME. This caused an exception to be thrown before the
ARDUINO_HOME existence check had executed.
Merge pull request #11 from mmurdoch/master

Check ARDUINO_HOME before use on Windows
Some fixes for run on gentoo amd64
Merge branch 'master' of github.com:rshk/arscons