Changed 'hasAttribute' function to 'getAttribute' function in Danger.js

I have changed the 'hasAttribute' function to 'getAttribute' in Danger.js. The hasAttribute function was the only thing causing React to not work in IE7 when using the appropriate shims. 

I tried to find a shim/sham to accomplish this, but it doesn't seem like it can be accomplished with it. 

All tests pass, the lint doesn't, but it doesn't pass in master either.