Removed non-7 bit ACSII character

The é in Stéphane make catkin crash on my MacBook.

```
Traceback (most recent call last):
  File "/Users/dgossow/ros_catkin_ws/install_isolated/share/catkin/cmake/parse_package_xml.py", line 87, in <module>
    main()
  File "/Users/dgossow/ros_catkin_ws/install_isolated/share/catkin/cmake/parse_package_xml.py", line 81, in main
    lines = _get_output(package)
  File "/Users/dgossow/ros_catkin_ws/install_isolated/share/catkin/cmake/parse_package_xml.py", line 55, in _get_output
    values['MAINTAINER'] = '"%s"' % (', '.join([str(m) for m in package.maintainers]))
UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 2: ordinal not in range(128)
```