Add time-grunt

Shows elapsed time of tasks at the end.

https://github.com/sindresorhus/time-grunt
Making autoprefixer a default
Remove unused vendored bootstrap.js
Add prompt for grunt-modernizr
Allow font files in sub-folders
Merge pull request #128 from passy/modernizr

Add prompt for grunt-modernizr
Merge pull request #122 from felquis/allowFontFilesInSubFolders

Allow font files in sub-folders
Fixed requirejs + bootstrap

Broke in 9bddba912184b12157c8b93f945574fe288d6442
Add --skip-install-message, --skip-welcome-message
Merge pull request #125 from passy/skip-flags

Add --skip-install-message, --skip-welcome-message
Modernizr is no longer included by default
Revert "Modernizr is no longer included by default"

This reverts commit 9ccb370e9619da4e2f2125693802a72a77e20497.
Corrected: dropping Modernizr from defaults
add grunt-bower-install. closes #121.