use vim and vimdiff

this patch adds vimdiff as diff programm
it also adds a command edit that will open the local file of an
id in the configured editor (i.e., vim).
The script uses redirections to and from /dev/tty which look a bit odd.
Maybe there is a better way.
Merge branch 'master' into useVimdiff
remove unneccessary stdout redirect
accept whitespaces in mapping file
change config file name to .deployrc
update README.md

add "edit" command
explain commands
add an error message of no matching id was found
Revert "add an error message of no matching id was found"

This reverts commit 128fc50550b4528a42115fe0166da4beaaa541f5.

Error message didn't work because counting the matches happens in
a different process.
allow directories to be deployed
Merge branch 'use-vimdiff'