[addon attach] Implement detach method (Bump to 0.20)

bower.json

@@ -1,5 +1,5 @@
 {
   "name": "xterm.js",
-  "version": "0.19",
+  "version": "0.20",
   "ignore": ["demo", "docs", "test", ".gitignore"]
 }

docs/conf.py

@@ -51,9 +51,9 @@ copyright = u'2014, SourceLair Limited'
 # built documents.
 #
 # The short X.Y version.
-version = '0.19'
+version = '0.20'
 # The full version, including alpha/beta/rc tags.
-release = '0.19 Alpha'
+release = '0.20 Alpha'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.