Values that contained ": " would not be parsed correctly for copying to
the clipboard. If, for example, a password contained ": ", those
characters and any following them wouldn't be copied. This change allows
such passwords to be copied correctly.

Enumerate the commands available in the interactive interface and
describe what they do.

Include a Gif screencast displayed in the README.

Include a description of the program, how to use it, install and
uninstall instructions, and license information.

A placeholder Demo section is also written in where a short screencast
is expected to be inserted.

Also include brief notices in the source files. Not a fan of the huge
blocks of text that the FSF recommends.

Create a Bash completion file that refers to the
`_pass_complete_entries` function from the `pass` Bash completion file.
The same completion options are given as when using `pass show`.