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.
Extend noop-commands list

Closes #239, #208
front-end: remove unusable tabs in settings screen
front-end: rename "(no domain)" to "(node natives)"
front-end: hide DOM and Event Listener breakpoints

Closes #186