Version 3.2.0

Core changes:
* Allow g:syntastic_filetype_map to apply to composite filetypes (@lcd047)
* Re-read g:syntastic_mode_map at each attempted check (@lcd047)
* New config variable g:syntastic_delayed_redraws (@lcd047)
* New config variable g:syntastic_id_checkers (@lcd047)
* Various bugs have been fixed.

Syntax checker changes:
* Added swiffer checker for Dust.js (@smfoote)
* Rework of the gcc checkers (@lcd047)
* Rework of the perl checker (@lcd047)
* Added handlebars checker for Handlebars (@mutewinter)
* Added foodcritic checker for Chef (@dougireton)
* Added rubylint checker for Ruby (@YorickPeterse)
* Added shellcheck checker for sh (@lcd047)
* Added scss_lint checker for SCSS (@sds)
* Various bugs have been fixed.