BF - Grab Basis Functions in column names to specify contrasts

Following [this discussion](http://mail.scipy.org/pipermail/nipy-devel/2013-February/008731.html) on the Nipype dev list, columns specified by both name and basis function were not being matched correctly by the SPM EstimateContrast interface and were raising "Condition Not Found" errors when fully specified (e.g. "condition*bf(2)"). 

This fix adds a matched group when matching on basis functions that allows contrast tuples like:

```python
('ConditionA', 'T', ['conditionA', 'conditionA*bf(2)', 'conditionA*bf(3)'], [1,1,1])
```

The PR includes a bug-fix to treat unicode as a string when writing SPM jobs.