Add unit test for overriden to() method

[mjauvin]

ref: wintercms/wn-translate-plugin#36 (comment)

[arvislacis]

Although added test looks valid and useful, the actual result of failed cases is the same, I mean, if you decode https://www.example.com/path?array%5B%5D=v1&array%5B%5D=v2 then it's equal to https://www.example.com/path?array[]=v1&array[]=v2

Problems starts with https://www.example.com/path?array[0]=v1&array[1]=v2 which is then interpretated as https://www.example.com/path?array[0][]=v1&array[1][]=v2

[mjauvin]

@arvislacis Yes, I am aware of this, but @LukeTowers needed a test case that showed the issue in order to fix the problem.

[LukeTowers]

Merged in 32df10c