Add build/Release to Node gitignore

This re-covers the http://nodejs.org/api/addons.html case for which the "build" directory was added in 00686415c4, but doesn't break cross-environment projects that use the build directory for including concatenated/minified source. Mazel tov!

Node.gitignore

@@ -23,6 +23,9 @@ lib-cov
 
 # Node-specific patterns
 
+## Compiled binary addons (http://nodejs.org/api/addons.html)
+build/Release
+
 ## Dependency directory
 ## Deployed apps should consider commenting this line out:
 ## see https://npmjs.org/doc/faq.html#Should-I-check-my-node_modules-folder-into-git