Version 3.4.0

Core changes:

* Remove g:syntastic_delayed_redraws (@lcd047)
* New options *_before and *_after for makeprgBuild() (@lcd047)
* New jump mode for g:syntastic_auto_jump (@lcd047)
* New buffer-local user variables b:syntastic_<filetype>_<checker>_<option> (@lcd047)
* Overhaul of the checker registry (@lcd047)
* Speed optimisations (@lcd047)
* Various bugs have been fixed.

Syntax checker changes:

* Disable the perl checker by default, for security reasons (lcd047)
* Remove support for YouCompleteMe (@lcd047)
* Added vimlint checker for VimL (@lcd047)
* Added bemhtmllint checker for BEMHTML (@SevInf)
* Added frosted checker for Python (@sergeybe)
* Added code-ayatollah checker for Racket (@lcd047)
* Added makeinfo checker for texinfo (@lcd047)
* Added avrgcc checker for AVR sources (@karel-)
* Added gcc checker for AT&T and Intel assembly files (@jrahm)
* Added syntaxerl checker for Erlang (@locojay)
* Added jsxhint checker for JSX (@thomasboyt)
* Various bugs have been fixed.