Added rule noRedundantBodySelectors.

Signed-off-by: matematik7 <domen.ipavec@z-v.si>
Added some helper functions and rewritten two rules with them.

Signed-off-by: matematik7 <domen.ipavec@z-v.si>
Added tests for noRedundantChildSelectors.

Signed-off-by: matematik7 <domen.ipavec@z-v.si>