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
@pixunil if you put a file in /share/goodie/my_ia/my_ia.css it'll be automatically included, see: https://duck.co/duckduckhack/code_styleguide#css