LearnBoost/stylus — pull request #793 by mekto (2012-08-17 00:22:28+00:00)
Title: 'while' loop support

Stylus has 'for' loops, but there are cases where the number of iterations is not known at the start of a loop (depends on inside calculations).

Example from 'modular-scale' module I'm trying to do (not possible with 'for' loops):

```
i = -1
v = size * (ratio ** i)
while v > base
push(results, v)
i -= 1
v = size * (ratio ** i)
```

This pull request contains tests and implementation.