* Add index preprocessor
README.md is a de facto index file in markdown-based documentation.
Hence, we respect to README.md and convert it into index.html.
* Fix warning for unused variables
* Update tests for config
* Match file stem case-insensitively for IndexPreprocessor
* Add tests for IndexPreprocessor
* Update book example to fit index preprocessor
* 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
Weihang Lo
Michael Bryan
Jaime Valdemoros
Michal Budzynski