Move enable/disable to parent Package class

This was previously unimplemented in TextMatePackage causing exceptions
when trying to enable/disable a package of that type.

src/atom-package.coffee

@@ -52,12 +52,6 @@ class AtomPackage extends Package
         console.warn "Failed to load package named '#{@name}'", e.stack ? e
     this
 
-  enable: ->
-    atom.config.removeAtKeyPath('core.disabledPackages', @metadata.name)
-
-  disable: ->
-    atom.config.pushAtKeyPath('core.disabledPackages', @metadata.name)
-
   reset: ->
     @stylesheets = []
     @keymaps = []

src/package.coffee

@@ -47,6 +47,12 @@ class Package
   isActive: ->
     atom.packages.isPackageActive(@name)
 
+  enable: ->
+    atom.config.removeAtKeyPath('core.disabledPackages', @metadata.name)
+
+  disable: ->
+    atom.config.pushAtKeyPath('core.disabledPackages', @metadata.name)
+
   isTheme: ->
     !!@metadata?.theme