bad syntax highlighting in multiline string in curtsies

```
#!python

>>> s = """a
... bcd
... efg"""
```

incorrectly highlights `a` and `efg`.

---
- Bitbucket: https://bitbucket.org/bobf/bpython/issue/266
- Originally Reported By: [ ](http://bitbucket.org/thomasballinger)
- Originally Created At: 2014-03-05T22:17:42.448
