* Add search with elasticlunr.js
This commit adds search functionality to mdBook, based on work done by @phaiax. The in-browser search code uses elasticlunr.js to execute the search, using an index generated at book build time by elasticlunr-rs.
* Add generator comment
Someone on Reddit was wondering how the rust book was generated and said they checked the source. Thought I'd put this here. Might be a good idea to have a little footer "made with mdBook", but this'll do for now.
* Remove search/editor file override behavior
* Use for loop for book iterator
* Improve HTML regex
* Fix search CORS in file URIs
* Use ammonia to sanitize HTML
* Filter html5ever log messages
* Added documentation to the `config` module
* Added an example to the `config` module
* Updated the docs in lib.rs regarding implementing backends
* Started writing an alternate backends walkthrough
* Mentioned the output.foo.command key
* Added example output
* Added a config section to the backends tutorial
* Finished off the backends tutorial
* Made sure travis checks mdbook-wordcount
* Fixed the broken link at in the user guide
* Changed how travis builds the project
* Added a conclusion
* Went through and documented a lot of stuff
* Added a preprocessors chapter and updated For Developers
