Libzim

============

* [Writer] Index the articles in differents threads. This is a huge speed
improvement as the main thread in not blocked by indexing.
* Index the title only if `shouldIndex` return true.

============

* Improve indexation of the title.
* Better pertinence of suggestions (only for new zim files)
* Improvement of the speed of Leveinstein distance for suggestions (for old
zims)

============

* Improve README.
* Remove gtest as embeded subproject.
* Better lzma compression.
* Better performance of the leveinstein algorithm (better suggestions
performance)

============

* Update README.
* [Writer] Add debug information (print progress of the clusters writing).
* [Writer] Correctly print the url to the user.
* [CI] Add code coverage.

============

* Fix thread slipping for win32 crosscompilation.
* Fix a potential invalid access when reading dirent.
* Fix memory leak in the decompression algorithm.
* [Writer] Fix a memory leak (cluster cleanning)
* [Writer] Write article data in a temporary cluster file instead of a
temporary file per article.
* [Writer] Better algorithm to store the dirent while creating the zim
file. Better memory usage.
* [Writer] [API Change] Url/Ns are now handle using the same struct Url.
* [Writer] [API Change] No more aid and redirectAid. A redirectArticle
have to implement redirectUrl.
* [Writer] Use a memory pool to avoid multiple small memory allocations.
* [Writer] [API Change] Rename `ZimCreator` to `Creator`.
* [API Change] File's `search` and `suggestions` now return a unique_ptr
instead of a raw pointer.

============

* Build libzim without rpath.