bashrc: Use gvim as EDITOR

Must provide "-f" since it has to stay in the foreground for git
messages, otherwise it will always exit with an "aborting due to no
message"-message.

Signed-off-by: Carl Helmertz <helmertz@gmail.com>
readme: Reminder of gitconf's log.decorate

It's good for you.

Signed-off-by: Carl Helmertz <helmertz@gmail.com>