Legacy Modes

This release changes the way that legacy modes are exported. Now, you import legacyModes, which has properties on it for each legacy mode.

This is in preparation for splitting out legacy modes into their own separate package (#6 ).

The import structure is as follows (as shown in demo):

let {                       
  EditorState,                 
  EditorView,
  keymap,                      
  history,                     
  redo,
  redoSelection,               
  undo,
  undoSelection,
  lineNumbers,                 
  baseKeymap,
  indentSelection,             
  legacyMode,
  legacyModes: { javascript },
  matchBrackets,
  specialChars,
  multipleSelections           
} = CodeMirror;