chore: add IDE temporal files to .gitignore file
chore: add .jshintrc file for javascript code quality
chore: Rebuild the build system

The previows build system in gulp was broken, the entire system has been replaced with grunt. To create the distributable files simply run 'grunt' after the build is complete a watcher is started. Alternatively you can run
'grunt build-css' to build only the CSS files and 'grunt build-js' to build only the Javascript files.

BREAKING CHANGE: Replace Gulp with Grunt
refactor: Change the way we set media queries dynamically

The previous code produce a parse error in the stylus compiler, this change the way we set media queries. Use variables insead of functions.
refactor: delete prefixer mixin

The CSS property prefixing is done automatically in the build process, a mixin for this purpose is not longer needed
refactor: replace font-size mixin, use pxToRem() instead

The previous mixing adds a font-size rule with a rem unit and a px fallback, this is redundant for someone who doesn't need support for IE8.
Also adds a line height depending of the font-size, we left this to the developer. Now instead of add a font-size rule we just convert px to rem to maximize reutilization.

BREAKING CHANGE: 'font-size' mixing deleted, use 'pxToRem' instead
fixed: 'grid-setup' mixin now works
fix: 'push-setup' mixin now works
fix: 'pull-setup' mixin now works
fix: attribute selectors with stylus in _grid.styl now works
fix: set proper format to variable asignment in _main.styl, delete unnecessary variable
refactor: update use of 'breakpoint' mixin, now use @media instead
fix: change @page format for stylus
refactor: delete use of 'vendor' mixing, the process is done in the build process instead
refactor: delete use of 'vendor' mixing & change syntax

vendor prefixing is done in the build process, also some problematic
syntax is fixed
fix: unquote filter value (stylus)

http://stackoverflow.com/questions/6593683/stylus-parseerror-expected-indent-got-outdent
:
"Stylus has a build-in alpha function so you need to escape it with
unquote"
fix: clean .editorconfig, prevents parsing error
refactor: use pxToRem() instead of font-size()
refactor: use @media instead of breakpoint()
refactor: delete use of vendor()