Corrected org agenda files in helpfile

Hi, I started to use your VimOrganizer recently. I'm appreciating your work.

The variable g:org_agenda_files written in the helpfile, doc/vimorg.txt, doesn't seem to work.
Checking ftplugin/org.vim, the description should be replaced by g:agenda_files.
In addition, unspecified characters, whose character codes are 0x91, and 0x92, are included in the text, and they are removed.

Could you check them?
Regards.