replace should.js with chai
use sinon-chai for nicer assertions on spys
make rendr-handlebars a devDependency

the rendr-handlebars module it is only required for running the tests.
Merge pull request #170 from c089/replace-should-with-chai

Replace should with chai
fix syntax error in package.json
Point to grunt-contrib-handlebars@~0.5.11
reenable view.attributes from backbone
Merge pull request #172 from lusini/add-view-attributes-object

Reenable View.attributes from Backbone
Merge pull request #171 from c089/make-rendr-handlebars-a-devDependency

make rendr-handlebars a devDependency