Merge snippets between theme and basetheme

- Current theme has preference over the base theme
- Snippets with the same name are overwritten by the current theme.
- If the overwritten snippet has no `gen` property (or `gen` is falsy), it will remove the base Theme snippet.
- Snippets not overwritten will carry over from base Theme
- New snippets will be added on to base Theme

client/homebrew/editor/editor.jsx

@@ -248,6 +248,7 @@ const Editor = createClass({
 					onInject={this.handleInject}
 					showEditButtons={this.props.showEditButtons}
 					renderer={this.props.renderer}
+					theme={this.props.brew.theme}
 					undo={this.undo}
 					redo={this.redo}
 					historySize={this.historySize()} />