Update README.md
feat(promiseTracker): add tracker.tracking() method

tracker.tracking() provides information whether the tracker is currently
tracking a request. This even includes requests that are not considered
active due to the `activationDelay`.
test(promiseTracker): add tests for tracker.tracking()
release(): v2.0.1
Update README.md
Update README.md
Update README.md
Update README.md
Fixed typo
Merge pull request #53 from daviesgeek/patch-1

Fixed typo
Merge branch 'master' of https://github.com/ajoslin/angular-promise-tracker