Added Modernizr 2.7.0 dev and custom build, tweak package.json

Source: http://modernizr.com/downloads/modernizr-latest.js and
http://modernizr.com/download/#-fontface-backgroundsize-borderimage-borderradius-boxshadow-flexbox-hsla-multiplebgs-opacity-rgba-textshadow-cssanimations-csscolumns-generatedcontent-cssgradients-cssreflections-csstransforms-csstransforms3d-csstransitions-applicationcache-canvas-canvastext-draganddrop-hashchange-history-audio-video-indexeddb-input-inputtypes-localstorage-postmessage-sessionstorage-websockets-websqldatabase-webworkers-geolocation-inlinesvg-smil-svg-svgclippaths-touch-webgl-shiv-cssclasses-addtest-prefixed-teststyles-testprop-testallprops-hasevent-prefixes-domprefixes-load

Development version (modernizr.dev.js) added and minified. Custom version (modernizr.js) functionality tallies with 2.6.2 and also 2.7.0 default download, so leaving as-is.

Added 2x developers and updated short description (taken from http://modernizr.com lead copy).