Reverse ConvertibleTo check to avoid panic

in `ObjectsAreEqual`, `expectedValue.Convert(actualType)` was being called when
`actualType.ConvertibleTo(reflect.TypeOf(expected))` was true.  This was a problem
for situations such as when expected was an int and actual was a string, since
ints are `ConvertibleTo` strings, but the reverse is not true.

Changing the ConvertibleTo check to `expectedValue.Type().ConvertibleTo(actualType)`
solves the issue.

assert/assertions.go

@@ -37,8 +37,8 @@ func ObjectsAreEqual(expected, actual interface{}) bool {
 	}
 
 	actualType := reflect.TypeOf(actual)
-	if actualType.ConvertibleTo(reflect.TypeOf(expected)) {
-		expectedValue := reflect.ValueOf(expected)
+	expectedValue := reflect.ValueOf(expected)
+	if expectedValue.Type().ConvertibleTo(actualType) {
 		// Attempt comparison after type conversion
 		if reflect.DeepEqual(actual, expectedValue.Convert(actualType).Interface()) {
 			return true