Silince UnicodeWarnings in tests

Fixes warning like the following in the test output:
```
/home/travis/virtualenv/python2.7.8/lib/python2.7/site-packages/matplotlib-1.5.x-py2.7-linux-x86_64.egg/matplotlib/text.py:52: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
  if rotation in ('horizontal', None):
```

The changes are somewhat stupid and redundant and the only purpose is to fix the warnings. 
I think this bit of logic should be written as:

```python
try:
   angle = float(rotation)
except ValueError:
    if rotatation is None or rotation == 'horizontal':
        angle = 0
   elif rotation == 'veritcal':
       angle = 90
   else:
       raise ValueError("some message")
```
or

```python
rotation_key_dict = {None: 0, 'horizontal': 0, 'verticale': 90}
try:
    angle = rotation_key_dict[rotation]
except KeyError:
    angle = float(rotation)
```