(De)serialization of `RangeInclusive`

[rocallahan]

I wrote an implementation of Serialize here: https://github.com/rocallahan/serde/tree/range-inclusive

But I can't get tests to run with unstable features:

[roc@glory test_suite]$ cargo test --features unstable
    Finished dev [unoptimized + debuginfo] target(s) in 0.0 secs
     Running /home/roc/serde/target/debug/deps/compiletest-a1e4ab2536d42e20
/home/roc/serde/target/debug/deps/compiletest-a1e4ab2536d42e20: error while loading shared libraries: libtest-b48219465f029877.so: cannot open shared object file: No such file or directory
error: test failed

I haven't got time to dig into this further.

[dtolnay]

Implemented in #1347.