Common git commands, --reencrypt, --force.

New features:

  * command name completion (show,insert,generate,etc)

  * `pass init <tab>` will list email addresses from gpg --list-keys

  * for 'show' command, if a folder contains a single entry, it will be
    auto-completed (recursively!)
    The other commands don't do this since you could be adding a new
    entry into an existing folder.

  * option completion (e.g., --clip)

Note: I turned off "-o filenames" because it was incompatible with the
auto-expansion. So, I instead quote using `printf "%q"` to handle files
with spaces and other odd characters.

Import passwords as multiline entries with password in the first
line. Rest contains following data if they exist in the entry element
of the xml file:

- username
- url
- comment

This should be removed at somepoint in the future. Currently, the
Homebrew people need something to make them happy. This is it.

this allows the full entry to be completed with a single tab if there is
only one entry in a folder

e.g., given:

 amazon.com
     user at domain.com
 google.com
     user1
     user2

`pass am<tab>` -> `pass amazon.com/user at domain.com`

while

`pass goo<tab>` -> `pass google.com/`

(previously, the amazon completion would have stopped at amazon.com
despite only a single entry existing)

this allows completing password entries without explicitly typing 'show'