Make property tests work again

[MansurAshraf]

Tests were not running before. This change ensure tests are running (but not necessarily passing ...yet)

[johnynek]

Looks good to me, but question: how can we be sure the tests are all running now? Can we set scalatest to error if you have a property that never asserts?

[MansurAshraf]

I inverted the assert conditions in BaseProperties and made sure that tests run and fail.

[johnynek]

@MansurAshraf cool. Can you comment on what the PR in #197 should do to be compatible with this style?

[johnynek]

The URL injection test failed. It is flakey. Can you switch it from using the default Arbitrary.arbitrary[String]: Gen[String] to something like:

Arbitrary.arbitrary[String].filter(s => Try(new Url(s)).isSuccess)

then we only start with strings that won't throw.

[johnynek]

Thanks for doing this! Next stop: code coverage.