[theme] Fix color problem of steeef theme
[theme] Fix color problem of steeef theme

steeef theme sets colors depending on $TERM, however if %F is
used, it must be closed by %f instead of %{$reset_color%}.

Further on, all %f directives have been replaced by %F and color
support of current TERM is checked more properly.

nunogt/oh-my-zsh,FrankSansC/oh-my-zsh,FrankSansC/oh-my-zsh,tekniklr/oh-my-zsh,nunogt/oh-my-zsh,FrankSansC/oh-my-zsh,tekniklr/oh-my-zsh,FrankSansC/oh-my-zsh