Issue #134 add message about actual value when assertion failed

During todays hackaton at @pragmatists we added displaying message about actual value when assertion failed for: `isEqualToComparingFieldByField`, `isEqualToIgnoringGivenFields`, `isEqualToIgnoringNullFields`, `isEqualToComparingOnlyGivenFields`. 

`isEqualToComparingFieldByField` was the subject of the issue. Others (similar cases) were needed to eliminate compilation errors and to make change consistent.