Fix Karma using hardcoded browsers

[nechaido]

Currently build fails on my PC due to this issue:

10 05 2017 19:29:18.230:ERROR [launcher]: No binary for ChromeCanary browser on your platform.
  Please, set "CHROME_CANARY_BIN" env variable

npm output

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! metarhia-jstp@0.7.0-pre test-unit-browser: `karma start`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the metarhia-jstp@0.7.0-pre test-unit-browser script 'karma start'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the metarhia-jstp package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     karma start
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs metarhia-jstp
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls metarhia-jstp
npm ERR! There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/nechaido/.npm/_logs/2017-05-10T16_29_23_391Z-debug.log
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! metarhia-jstp@0.7.0-pre test-unit: `npm run test-unit-node && npm run test-unit-browser`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the metarhia-jstp@0.7.0-pre test-unit script 'npm run test-unit-node && npm run test-unit-browser'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the metarhia-jstp package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     npm run test-unit-node && npm run test-unit-browser
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs metarhia-jstp
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls metarhia-jstp
npm ERR! There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/nechaido/.npm/_logs/2017-05-10T16_29_23_405Z-debug.log
npm ERR! Test failed.  See above for more details.