fix: Look for other paths for Firefox Nightly on Windows and Mac
fix: Look for other paths for Firefox Nightly on Windows and Mac

More recent installs of Firefox Nightly on Windows use "Firefox Nightly"
instead of "Nightly" for the application folder. Apparently OSX uses
"Firefox Nightly" instead of "FirefoxNightly" too.
karma-runner/karma-firefox-launcher,karma-runner/karma-firefox-launcher