Config builder `tab-size` out of date.

[elidupuis]

I just used the online config builder (which is awesome!). Afterwards, when I ran csscomb, I got a warning:

Failed to configure "tab-size" option:
The option does not accept values of type "boolean".
Value's type must be one the following: number.

It appears that the config builder set "tab-size": true. I updated this to my desired value as a number and the error went away "tab-size": 2.