Fix for Issue #36 "Brackets of different types matched"

* use a nicer variable name

* reuse $pos instead of using another variable
* remove declaration forgotten in last commit

Fix for Issue #35 "Unclosed brackets not marked as error"

* Allow to override highlighters directory through `ZSH_HIGHLIGHT_HIGHLIGHTERS_DIR`
* Handle spaces in the directory path
* Use Zsh builtin "h" modifier instead of `dirname`

Error: "unrecognized modifier 'A'" on startup for zsh 4.3.9 on OSX

Much easier and less error prone way to start highlighting immediately af

Conflicts:
	zsh-syntax-highlighting.zsh

* 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

Originally, zsh-syntax-highlighting called highlight functions at every inputs.
It's OK for user's keyboard inputs. But when long inputs come from clipboard,
it cause noticeable slowdown.

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

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>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Markdown for everyone

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Julien Nicoulaud <julien.nicoulaud@gmail.com>

Signed-off-by: Takeshi Banse <takebi@laafc.net>

For easily extending the highlighting behavior, split the
actual highlighting function into some pieces.

For example "_zsh_main-highlight" transformed into,

1) An actual highlighting function which updates the
`region_highlight` on its own. (_zsh_main-highlight)
2) A predicate which determines whether its highlighting function
(in this case `_zsh_main-highlight`) should be called or not.
(_zsh_buffer-modified-p)

Likewise, `_zsh_highlight-bracket-match` and
`_zsh_highlight-bracket-match-p` are born.

Eventually, `_zsh_highlight-zle-buffer` coordinates above these
functions and maintain some internal state variables.

Finally, added `_zsh_add-highlighter` a little syntactic-sugar-ish
function to register the highlighting functions in an appropriate manner.

Signed-off-by: Takeshi Banse <takebi@laafc.net>

Append it to ZSH_HIGHLIGHT_FUNCTIONS.

Signed-off-by: Takeshi Banse <takebi@laafc.net>

Make `_zsh_highlight-zle-buffer` just a hands-off.
Now, `_zsh_highlight-zle-buffer` calls each ZSH_HIGHLIGHT_FUNCTIONS
in turn.  The former `_zsh_highlight-zle-buffer` is renamed to
`_zsh_main-highlight.`

Signed-off-by: Takeshi Banse <takebi@laafc.net>