fix the timex bug when may and sat appear as verbs instead of timexes

[qiangning]

Previously, to avoid silly mistakes, I incorporated rules before timex chunker, so that any word matching to month names or week-of-the-day names will be forced to be a timex.

However, I realized that this rule is not accurate. may can be either a modal verb, or the month. sat can be also the past tence of sit. So I have added a POS check now: only those may's or sat's that are NNP will be forced to be timex.

sun is a bit tricky, since the star Sun is also NNP. I pick it out of our rules and leave it up to the chunker's decision.

[qiangning]

Daniel @danyaljj, Mark @mssammon : I suggest Zhili @666666fzl review this change.

[powpos360]

LGTM

[qiangning]

@danyaljj I've merged this PR. Since this is my first time merging PRs, are there anything else I need to do after the merge?

[danyaljj]

Nope. You're good.

Note that the change is not deployed yet. In other words, the jar files in the maven repo (http://cogcomp.org/m2repo/edu/illinois/cs/cogcomp/) still don't contain your changes. We deploy only when there is a need for doing so. If you need it, you have to deploy it (details here)