wordy PHP assignment

## Unit Tests

`% php phpunit.phar --testdox wordy/wordy_test.php`

```
WordProblem
 [x] add 1
 [x] add 2
 [x] add negative numbers
 [x] add more digits
 [x] Subtract
 [x] Multiply
 [x] Divide
 [x] add twice
 [x] add then subtract
 [x] subtract twice
 [x] subtract then add
 [x] multiply twice
 [x] add then multiply
 [x] divide twice
 [x] too advanced
 [x] Irrelevant
```