remove unused dependency on term

[soruh]

This PR removes the unused dependency on term which is no longer maintained and has a RUSTSEC advisory.
Having the term dependency causes warnings when running cargo audit in reverse dependencies.

[MightyPork]

@bradfier this and #231 seem safe to merge despite the travis error, I just tried it. Could you look into it when you have time?

Rouille now drags 2 years old versions of dependencies into our project, I'm trying to reduce the attack surface using cargo deny...

[bradfier]

It seems quite reasonable indeed, I can't modify the original PR branch but I'll rebase this commit onto master and run the new test suites.

[bradfier]

Merged as 45f1631