Add detect() method for the tab-size.js

[drugan]

To reproduce:

Put mystyle.css into the project root directory.
mystyle.css.txt

Run:
csscomb -d mystyle.css

Observe:

Apply the current PR changes, run the command again and observe:

[tonyganch]

Hey @drugan, builds for your detect PRs seem to be failing. Could you please take a look?

[drugan]

The culprit was in test/options/integral/detect/test.js. This file uses the default csscomb.json to check options' values against but it does not have tab-size option though with the current patch the respective value is detected.

Also, the logic for detect() in the tab-size.js is improved (hopefully).

[mariovalney]

Hi! Me again again 😄

Would you can refresh this too?