Manage tabs without webNavigation

[ShaneHarvey]

Using the webNavigation API displays this permission to users "Read your browsing history." This would likely turn users away from installing because it makes StopLeak seem fishy.

We either can use tabs.onUpdated and tabs.onCreated or use "main_frame" requests (in webRequest.onBeforeRequest) to replace the functionality of webNavigation.onCommited.