Node Sass 3.4.0

[xzyfer]

This PR updates to the stable node-sass@^3.4.0.

It also updates the error messages to use LibSass pre-formatted errors. This means gulp-sass will now produce the exact same error messages as LibSass, node-sass, and grunt-sass.

Before

test/scss/error.scss
property "font" must be followed by a ':'

After

test/scss/error.scss
Error: property "font" must be followed by a ':'
        on line 2 of stdin
>>   font 'Comic Sans';
   --^

[mathiasbynens]

Could you npm publish a new version of gulp-sass containing these changes please?

I’m currently using git://github.com/dlmanning/gulp-sass.git#d7ca6a45e89ce878645c6c0582407452899bd7c7 as a dependency which feels kind of dirty.

[xzyfer]

@mathiasbynens we're tracking the next release in #375

Unfortunately there are some issues with the latest LibSass we want to get sorted first.