Add support for custom browser events, closes #23

Currently google chrome (and hopefully other browsers as well soon)
support the `window.performance.mark` method which adds a custom event
to the event timeline. This patch allows wbench to report timings for
all of the custom browser events that are triggered during the load
process.
Readme formatting fixes
Bump to version 1.0.0
Add support for setting cookies. Currently this needs an extra visit to the homepage in order to set them for the correct domain.
Refactor cookie setting logic and use selenium add cookies method
Add information about setting cookies
Merge branch 'cookie_support'
Bump to version 1.1.0
Fix small error in readme