Fix exception when using Rule classes

[ivan770]

Fix ErrorException : substr() expects parameter 1 to be string, object given when using object classes in Form Requests

[mtrajano]

Hello thank you for the for the pr, I will take a look at it tonight. In the meantime would you mind adding a test to validate the fix? Thanks once again!

[mtrajano]

Also wondering if this is breaking for closure validation as well, we may just want to check that the rule is a string. Please see #14

[mtrajano]

This has been fixed with #14 and should be working as of v0.6.1. I like what you're doing with responses and think it can become a potential feature as some people have been asking for this, although it would probably require some small discussion. But please don't change anything with the authors or the package namespace. If you would like to become a maintainer we can talk about it.