%Ng formatting for floats not available as an option

```
The differences between %f and %g are described here:

http://stackoverflow.com/questions/5913102/what-is-the-difference-between-g-and-
f-in-c

I am attaching a simple program to illustrate some differences on real data.

Here is the output:

+---------------+------------------+--------------+-------------+
| default | floatFmt1 | floatFmt2 | gFmt |
+---------------+------------------+--------------+-------------+
| 123456789.123 | 123456789.123400 | 123456789.12 | 1.23457e+08 |
| 0.000122 | 0.000122 | 0.00 | 0.000122 |
| 23 | 23.000000 | 23.00 | 23 |
| 1.01010101 | 1.010101 | 1.01 | 1.0101 |
+---------------+------------------+--------------+-------------+

```

Original issue reported on code.google.com by `and...@andrewschein.com` on 24 Nov 2013 at 7:16

Attachments:
- [pretty.py](https://storage.googleapis.com/google-code-attachments/prettytable/issue-42/comment-0/pretty.py)

Start by running the attached pretty.py example and tracing the repository's float-formatting entry point to see how existing %f and %g-like options are handled. Done means providing a selectable %g-style format that produces the documented output for the sample values, with coverage for the requested behavior.

Written by the indexing model from the issue text.