SunInfo: add new Instant Answer for sunrise/sunset.

**What does your Instant Answer do?**

Computes the sunrise and sunset for a given day at the client's location.

**What problem does your Instant Answer solve (Why is it better than organic links)?**

Organic links don't generally work for arbitrary dates and may not know the client's location

**What is the data source for your Instant Answer? (Provide a link if possible)**

Uses [DateTime::Event::Sunrise]( https://metacpan.org/pod/DateTime::Event::Sunrise) from CPAN.

**Why did you choose this data source?**

Does not require network access.

**Are there any other alternative (better) data sources?**

Probably, but not for Goodie use.

**What are some example queries that trigger this Instant Answer?**

`sunrise`, `sunset`, `sunrise on aug 30`, `sunset on 2015-01-01`

**Which communities will this Instant Answer be especially useful for? (gamers, book lovers, etc)**

People who need to know when the sun rises or sets for scheduling purposes.

**Is this Instant Answer connected to a DuckDuckHack [Instant Answer idea](https://duck.co/ideas)?**

[Yes.](https://duck.co/ideas/idea/1200/sunrise-sunset-times)

**Which existing Instant Answers will this one supercede/overlap with?**

Supersedes the W|A answer for the "sunrise" and "sunset" bare queries, but provides more info than the W|A version. 

**Are you having any problems? Do you need our help with anything?**

I cannot presently use `duckpan` properly, so someone needs to confirm the HTML output and styling look correct.

**What does the Instant Answer look like? (Provide a screenshot for new or updated Instant Answers)**

Hopefully, it looks like the IP address info and unix epoch tables!

## Checklist
Please place an 'X' where appropriate.

```
[X] Added metadata and attribution information
[X] Wrote test file and added to t/ directory
[X] Verified that instant answer adheres to design guidelines (https://duck.co/duckduckhack/design_styleguide)
[X] Verified that instant answer adheres to code styleguide (https://duck.co/duckduckhack/code_styleguide)
[] Tested cross-browser compatibility


is this try needed? I thought we handled it in `parse_datestring_to_date` ?