fix compiling against node-webkit v0.11.0

+ recent atom-shell >= 0.18.0
replaced occurences of v8::Object::Set with 3 arguments with
v8::Object::ForceSet
add ci for node-webkit v0.11.0
fix building for node-webkit v0.11.0 on ia32
Merge pull request #369 from bwin/target-new-v8-from-chromium-38

Target new v8 from chromium 38
Linux and Mac builds for node-webkit v0.11.2 (released 2014-11-26)
Windows builds for node-webkit v0.11.2 (released 2014-11-26)
Merge pull request #378 from mapbox/support-node-webkit-0.11.2-on-windows

Build against node-webkit version 0.11.2