Throwing a proper RuntimeException when a property could not be loaded f...

...or a client because it didn't have a property name after the namespace

The load method throws a ```java.lang.StringIndexOutOfBoundsException``` currently for properties like this -

myclient.ribbon.=baz
myclient.ribbon=bar

This PR throws a ```java.lang.RuntimeException``` with the name of the property which is invalid in the message of the exception instead of the ```java.lang.StringIndexOutOfBoundsException```

We could also just log an error and load rest of the properties but this would change the current behavior where the method returns after throwing the ```java.lang.StringIndexOutOfBoundsException``` which also happens to be a subclass of ```java.lang.RuntimeException```
Or just check the message in the runtime exception instead of using the expected annotation. (ew?)