Update and tidy README

Removes references to defunct modernizr build generator
Removes repetition
Gulp -> gulp
https://github.com/gulpjs/gulp/blob/master/docs/FAQ.md#is-it-gulp-or-gulp
Removes references to Sass fork, it is dead
Removes "Organized file and template structure" as a feature
Some opinionated usage changes in the Contributing section
Adds my twitter to Readme so I can be reached for gulp stuff
Pimps bedrock
:beers: