More Google Reader keys

I added more Google Reader keys to googlereaderkeys plugin.

Additionally, there are 2 modifications in this pull request.
- Prevent interpreting as a hotkey prefix when modifiers pressed. d715d6a6dbe34140c44b9d7a659287c9c1e353a9
- Enable noscroll in noexpand. 8a58d10b569c52f8907371f3459c7dca3ee15558

The former one is behavior change, strictly speaking. However, I think almost no one expects a key with modifier keys should be considered as a prefix without modifiers. This modification is for `shift+a` hotkey.

The latter one is more subtle point. I'm not sure what is your actual intention. The 2nd argument of `cdmScrollToArticleId` seems to be to force scroll. So, it is natural to pass `!noscroll`. For me, this behavior is appropriate for `n` and `p` hotkeys.