Hyperlink crate items in docs

[twitu]

Rust docs makes it easy to hyperlink doc items by name. This makes it easier to navigate the docs because the reader can quickly jump to the definition of an item being referred.

That being said hyperlinking everything everywhere can make the docs look noisy and hinder readability. This is somewhat subjective but some general rules of thumb -

• Only need to hyperlink items in this crate
• If an items is mentioned multiple times in a paragraph or couple of paragraphs, hyperlinking the first time it's mentioned is good enough
• If a many items from a module are enumerated (like in bulleted list) hyperlinking the module is good enough

from discussion in #73