Fixed distance calculation, Re-written unoptimal code

Fixes bug in calculation distance between strings, distance was rounded down to integer number, e.g `3.9` -> `3`

```ruby
# was
mailcheck.suggest "user@juno.com" #-> 'user@msn.com'

# now - same as mailcheck.js
mailcheck.suggest "user@juno.com" #-> false
 
```


* Fixed distance calculation. 
* Re-written some unoptimal code
* Make code closer to style guide