Avoid using e notation

Unlike Lisp and JavaScript, JSON numeral syntax doesn't allow decimal points without decimal digits:

![number](https://cloud.githubusercontent.com/assets/3055134/5315346/99235fb4-7c7c-11e4-9e28-fc83d9acd980.gif)
(from http://www.json.org/fatfree.html)

```javascript
% node
> 1.e8
100000000
> JSON.parse("[1e8]")
[ 100000000 ]
> JSON.parse("[1.e8]")
SyntaxError: Unexpected token e
```
I think the easiest and safest solution is to prevent YASON from using e notation when encoding floats.