Fix python twitter

specify the version of python twitter (v0.8.5).

In order to avoid the following error:
```
HEAD is now at 07debf9 Merge pull request #168 from mafagafo/master
mkdir -p src; mkdir -p bin
mkdir -p /home/travis/build/jsk-ros-pkg/jsk_common/3rdparty/python_twitter/build/lib/python2.7/site-packages/
cd build/python-twitter && pip install --user -r requirements.txt
Could not open requirements file: [Errno 2] No such file or directory: 'requirements.txt'
Storing debug log for failure in /home/travis/.pip/pip.log
make: *** [installed] Error 1
```