Support more than just editors in the status bar

The status bar view now tracks the active pane item
and hides and shows elements that apply for the active
item such as path, cursor position, grammar, etc.

src/app/edit-session.coffee

@@ -156,6 +156,7 @@ class EditSession
   saveAs: (path) -> @buffer.saveAs(path)
   getFileExtension: -> @buffer.getExtension()
   getPath: -> @buffer.getPath()
+  getBuffer: -> @buffer
   getUri: -> @getPath()
   isBufferRowBlank: (bufferRow) -> @buffer.isRowBlank(bufferRow)
   nextNonBlankBufferRow: (bufferRow) -> @buffer.nextNonBlankRow(bufferRow)