Library evaluation tracking issue

[brson]

• Add a supertrait to hide trait details #69
• ByteOrder::default should panic! not unreachable! #68
• Put panic and error docs in "Panics" and "Errors" sections #72
• Make sure there are enough examples #75
• Add CI badges to Cargo.toml #74
• Add "categories" to Cargo.toml #73
• Add #[doc(html_root)] #77

This is the tracking issue for the evaluation performed by the libs team last week.

[BurntSushi]

Done! Thanks to @SamWhited!