Use Plot.ly

Update Plot.ly plot (http://plot.ly)
Change 'USER' and 'KEY' with your username + Api-Key
using realpath rather than hard coded
Merge pull request #1 from swooingfish/master

using realpath rather than hard coded
Update Readme with instructions for plot.ly
Merge branch 'master' of github.com:jensb89/PiTemp into jensb89-master