* Allow underscores in the link type name
* Add some tests for include anchors
* Include parts of Rust files and hide the rest
Fixes#618.
* Increase min supported Rust version to 1.35
* Add a test for a behavior of rustdoc_include I want to depend on
At first I thought this was a bug, but then I looked at some use cases
we have in TRPL and decided this was a feature that I'd like to use.
* Add docs for mdBook specific include feature.
Also:
* Fix bug in take_lines taking `end`-many lines instead of
`end-start` many.
* Handle special case `include:number` as including a single line.
* Start counting lines at 1 and not 0.
* Merge mdBook and rust specific features into one chapter.