* Don't override user defined styles
* Better modularisation of highlighters
* Allow to define which highlighters are activated
* Allow to define the order in which they are defined
* Minor performance optimizations
* Fixed some variables leak
* Improve documentation
* Brackets highlighter: use ZSH_HIGHLIGHT_STYLES instead of a specific array
The script still works on its own, highlighters in highlighters/ are
loaded as addons if present.
Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>