Update dependency to work on conda

requests_oauthlib dependency name will only install from pip, requests-oauthlib works on both conda and pip

setup.py

@@ -29,7 +29,7 @@ setup(name='mwclient',
       url='https://github.com/btongminh/mwclient',
       license='MIT',
       packages=['mwclient'],
-      install_requires=['requests_oauthlib', 'six'],
+      install_requires=['requests-oauthlib', 'six'],
       setup_requires=pytest_runner,
       tests_require=['pytest', 'pytest-cov', 'flake8',
                      'responses>=0.3.0', 'responses!=0.6.0', 'mock'],