Allow to install all binaries

[giggio]

I'd like to be able to install all binaries.

For example, when running:

 bin install github.com/gabyx/Githooks /tmp/githooks/bin/

3 binaries are found. I'd like an option so that all 3 to go to the /tmp/githooks/bin/ directory, something like --all-binaries.

 bin install --all-binaries github.com/gabyx/Githooks /tmp/githooks/bin/