Provide a convenient way of creating a binary package that can be
uploaded to the GitHub releases page.

To save me some time from having to write commands. Started with a
`reinstall` target to make it easier to put a new build on my PATH.

Then added a `test-all` target so I wouldn't have to use two commands to
run both test suites. Needed to create a `test` task also in order to
run the unit tests before the integration test.

Ensure that we `cargo build` before running integration tests. Otherwise
we might be testing against an old build.

Give us a task to run integration tests. This provides us with an
explicit definition of how these should be run, rather than me just
knowing that you have to run `prove` in order to execute them.