Update devtools overview url in README
Version checking refactored

Close #427.
test: increase test timeout in InjectorClient

The test setup takes more than 2 seconds in Travis CI, which caused the
build to fail. The timeout is 5 seconds now, which seems to be enough.
Profiler API

Realised full CPU Profiler API
- start
- stop
- getCPUProfile
- removeProfile
- clearProfiles
- getProfileHeaders
(squash) fixes to review