Handle errored and failing specs separately

An errored example is one that throws an exception that is not from an 
expectation failing.

src/spectator/errored_example_result.cr

@@ -0,0 +1,14 @@
+require "./failed_example_result"
+
+module Spectator
+  class ErroredExampleResult < FailedExampleResult
+    getter error : Exception
+
+    def errored? : Bool
+      true
+    end
+
+    def initialize(@example, @error)
+    end
+  end
+end

src/spectator/runner.cr

@@ -19,8 +19,10 @@ module Spectator
     private def run_example(example)
       example.run
       SuccessfulExampleResult.new(example)
-    rescue ex : Exception
-      FailedExampleResult.new(example, ex)
+    rescue failure : ExpectationFailedError
+      FailedExampleResult.new(example, failure)
+    rescue ex
+      ErroredExampleResult.new(example, ex)
     end
   end
 end