Add no_args support for stubs

Fixes https://github.com/icy-arctic-fox/spectator/issues/28

spec/issues/github_issue_28_spec.cr

@@ -0,0 +1,19 @@
+require "../spec_helper"
+
+Spectator.describe "GitHub Issue #28" do
+  class Test
+    def foo
+      42
+    end
+  end
+
+  mock Test do
+    stub foo
+  end
+
+  it "matches method stubs with no_args" do
+    test = Test.new
+    expect(test).to receive(:foo).with(no_args).and_return(42)
+    test.foo
+  end
+end