Don't crash on chunked response and turbolinks

Fixes issue #114
Merge pull request #115 from romanbsd/master

Don't crash on chunked response and turbolinks
update README and bump version
Track events weren't being sent asynchronously

Since options[:async] is usually nil and because we aren't merging defaults on to options (as we are in person.rb), options[:async] was nil and causing events to be tracked synchronously.
Merge pull request #116 from ericboehs/patch-1

Track events weren't being sent asynchronously