Added geometry formula shower / calculator Goodie

**What does your instant answer do?**
This goodie shows geometric formulas (e.g. circle area) or calculates them if sizes are specified.

**What is the data source for your instant answer? (Provide a link if possible)**
The german "Tafelwerk", because it is a good formulary

**What are some example queries that trigger this instant answer?**
formula circle area
for more: see test file

**Is this instant answer connected to a DuckDuckHack [instant answer idea](https://duck.co/ideas)?**
Yes, https://duck.co/ideas/idea/1053/geometry-calculator.

**Which existing instant answers will this one supercede/overlap with?**
Not known yet

**Are you having any problems? Do you need our help with anything?**
Not yet

- [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://github.com/duckduckgo/duckduckgo-documentation/blob/master/duckduckhack/styleguides/design_styleguide.md)
- [x] Tested cross-browser compatability *with support tables*; in brackets the feature which is used and has the lowest support for this browser
 - IE from version 9 (SVG)
 - Firefox from version 6 (data-*)
 - Chrome from version 7 (data-*)
 - Safari from version 5 (data-*)
 - Opera from version 11 (data-*)
- [x] Tested live only on Linux 64-bit, Firefox
For now, we tend to only use English in the instant answer code, unless absolutely necessary. We plan to translate instant answers eventually, but for now let's just stick with English. Otherwise, others might want to add translations and then the code will quickly become bloated.