rust/shed/hostname: rename hostname dependency to unbreak doctests (#15)

Summary:
Pull Request resolved: facebookexperimental/rust-shed#15

With the update from rustc 1.44 to 1.47 the doctests started to break when building a crate that depends on a different crate of the same name, see this: rust-lang/cargo#6819

This diff also removes the TravisCI build as it was broken and unused for some time.

Reviewed By: krallin

Differential Revision: D24390815

fbshipit-source-id: fa9c78ef394640afbf8c419f8276bbf339960406