New command defining format, minor improvements

- If the second address is empty, it is assumed to be `.`
- Regex addresses and `:substitute` now integrate with search history and
  respect case sensitivity settings
- Patterns for `:substitute` can't be delimited by
- `:set` now supports inverting options using `:set inv{option}` and
  `:set {option}!`
- New commands: `:new`, `:vnew`, `:exit`, `:xall`, `:wall`, `:qall`, `:update`

README.md

@@ -14,8 +14,11 @@ Use the service to register commands, from your own package, or straight from `i
 # in Atom's init.coffee
 atom.packages.onDidActivatePackage (pack) ->
   if pack.name == 'ex-mode'
-    Ex = pack.mainModule.provideEx()
-    Ex.registerCommand 'z', -> console.log("Zzzzzz...")
+    Ex = pack.mainModule.provideEx_0_30()
+    Ex.registerCommand
+      name: 'z'
+      priority: 1
+      callback: -> console.log('zzzzzz')
 ```
 
 See `lib/ex.coffee` for some examples commands. Contributions are very welcome!