Release Profile Optimisations

[mkroli]

This contains settings for the release profile which decreases the binary size from ~12M to ~4M on my machine.

[rossmacarthur]

Hi @mkroli, I don't think that binary size is necessarily the optimization that all users would benefit from. So with the exception of the strip flag I don't think we should change anything in the release profile. I am happy for an additional profile to be added that has these settings though, e.g. cargo install sheldon --profile compact. Alternatively, we could simply document the RUSTFLAGS that need to be set when running cargo install sheldon to accomplish this.