Merge pull request #482 from bt/master

Added ShouldBeError assertion
diff --git a/convey/assertions.go b/convey/assertions.go
index 1e87b82..b37f6b4 100644
--- a/convey/assertions.go
+++ b/convey/assertions.go
@@ -65,4 +65,6 @@
 	ShouldHappenWithin         = assertions.ShouldHappenWithin
 	ShouldNotHappenWithin      = assertions.ShouldNotHappenWithin
 	ShouldBeChronological      = assertions.ShouldBeChronological
+
+	ShouldBeError = assertions.ShouldBeError
 )