Fix for ShouldContainOnlyInOrder EnumerableAssertion extension that was broken when the collections were of different lengths (+pull request #6)

`ShouldContainOnlyInOrder` works only when the expected and actual collections have the same lengths. When expected is longer than actual, misleading `ArgumentException` is thrown instead of `SpecificationException`. When expected is shorter than actual, the assertion passes, but it shouldn't. 

This pull requests fixes the method to cope with those scenarios, leaving the other method's characteristics not touched. 

It also includes full [pull request #6](https://github.com/developwithpassion/developwithpassion.specifications/pull/6), basically to have the build running. But the core changes could be actually cherry-picked from the last commit.