Whitespace
Percentage Definition
Percentage param_name is configurable
Add test for deserializing a Percentage definition
Front-end changes for percentage rule

This should be decoupled
Address deprecation warning

```
lib/yodado/definition.ex:47: warning: crypto:md5/1 is deprecated and will be removed in in a future release; use crypto:hash/2
```
Memoize powers and improve digest_int/1

Thanks @madlep
Merge pull request #6 from envato/deterministic_percentage_strategy

Deterministic percentage strategy