Unable to specify optimization direction

It looks like you should be able to specify the direction of the optimisation (minimize or maximize) using the `optimizationDirection` property of the `CyClpSimplex` object:

https://github.com/coin-or/CyLP/blob/5c9a9dcb17809b99e14138e523c143a6000e8e14/cylp/cy/CyClpSimplex.pyx#L761

However, this property doesn't appear to be accessible from Python. There appears to be a test that checks for this, which currently fails on my machine.

```
======================================================================
ERROR: test_direction (__main__.TestCyClpSimplex)
----------------------------------------------------------------------
Traceback (most recent call last):
File "test_CyClpSimplex.py", line 59, in test_direction
self.assertEqual(self.s.optimizationDirection, 'min')
AttributeError: 'cylp.cy.CyClpSimplex.CyClpSimplex' object has no attribute 'optimizationDirection'
```