Fix #124: If an abstract rule is changed, run all rules

[UncleOwen]

Since I ran into this twice in short succession, I figured I might just as well fix this.

Applies a simple heuristic: If the name of a rule starts with 'Abstract', it's an abstract class. This could change any number of rules, so let's bail and just compare all rules.

My knowledge of ruby is very basic. I basically copied one of the other "compare all rules" test cases.

Fixes #124

[adangel]

merged via a7a756a

[zbynek]

@UncleOwen this does not cover classes that are in the internal package, but are not called Abstract*. On the other hand it treats some actual rules as abstract classes, such as AbstractClassWithoutAbstractMethodRule. I wonder if it would make sense to move all non-instantiable classes to the internal package and check only for internal.

[UncleOwen]

@zbynek I know. See the resolved discussion with adangel above.