add 'find-file-from-yank command and assign C-x y.

- find file the path from clipboards including OS X pasteboard.
remove needless codes.
Use package.el and refactor the whole .emacs.d

- Change directory assignment.
- Use init-elpa and 'require-package.
- Remove third-party libraries and require them on-demand.
  - Discard auto-install and use only package.el.
- Delete color-theme-solarized.