add gitignore, import nan to support node v0.11.x
Merge remote-tracking branch 'dead-horse/support-node_v0.11.x'

https://github.com/wadey/node-microtime/pull/15
require at least node 0.8.0
remove Tested on section, as it is out of date
remove 0.11 from travis until they update past 0.11.3
0.5.0