Session.js: accept() calls mediaHandler.render()
bower.json: bump version number to 0.6.0
package.json: add 'main: "dist/sip.js",'
package.json: bump version number to 0.6.0
package.json: change name to "sip.js", update Gruntfile.js accordingly

This disobeys an NPM tip: https://www.npmjs.org/doc/package.json.html#name
but avoids naming conflicts with https://www.npmjs.org/package/sip