Enable spelling in both US English and French
Download spelling files for English and French during setup

This step is not strictly necessary since user gets prompted
to download any missing file the first time spelling is enabled;
however, due to an error which is reported annoyingly each time
spelling is enabled [1] when using the default English word lists
included in Ubuntu and recent word lists for French from the download
site [2}, I decided to download preemptively more recent files in the
local folder ~/.vim/spell, which takes precedence over files from
the vim distribution located in /usr/share/vim/vimcurrent/spell/.

[1] Vim: Word characters differ between spell files (E763)
http://stackoverflow.com/questions/14802136/vim-word-characters-differ-between-spell-files-e763

[2] FTP archive directory /vim/runtime/spell
http://ftp.vim.org/vim/runtime/spell/