add tqdm to requirements

requirements.txt

@@ -7,3 +7,4 @@ scipy>=0.16
 pandas
 mock
 dill
+tqdm

setup.py

@@ -84,7 +84,8 @@ setup(name='bilby',
           'numpy>=1.9',
           'matplotlib>=2.0',
           'pandas',
-          'scipy'],
+          'scipy',
+          'tqdm'],
       entry_points={'console_scripts':
                     ['bilby_plot=cli_bilby.plot_multiple_posteriors:main',
                      'bilby_result=cli_bilby.bilby_result:main',