Some changes & Syned with linux-neobundle

* Added a comment ahead of file, to specified the presumptions
  (uncomplete)
* Added new plugins from linux-neobundle
    * vim-matrix-screensaver
    * vim-misc splitted from easytags
    * dbext
    * python-syntax
* Added initial vimwiki plugin configuration.
* several small configuration changes:
    * make 'ycm' not to register itself as syntastic checker.
    * make 'Mark' autosave marks.
    * set background=dark.