Correct display of month

Month displayed was incorrect, as JavaScript Date.getMonth() starts at 0. So November was displayed as '10'.
Correct display of month 

Month displayed was incorrect, as JavaScript Date.getMonth() starts at 0. So November was displayed as '10'.
Update README.md

Slightly pedantic grammar fix.
Merge pull request #531 from simonharris/master

Correct display of month on network graph