Print all args properly in final report

[clubby789]

Fixes #254

When invoked with cargo-bisect-rustc, our args look like
["cargo-bisect-rustc", "--start", ...]
However, when invoked with cargo bisect-rustc, our args look like
["/path/to/cargo-bisect-rustc", "bisect-rustc", "--start", ...]

Skip past these initial arguments instead of hardcoding the index

[ehuss]

Thanks!