Add missing dependency pyyaml in setup.py

Signed-off-by: Hiroshi Miura <miurahr@linux.com>

setup.py

@@ -21,7 +21,7 @@ setup(name='aqtinstall',
       author_email='miurahr@linux.com',
       packages=["aqt"],
       package_data={'aqt': ['*.yml', "*.json", "*.ini"]},
-      install_requires=['requests', 'six', 'py7zr'],
+      install_requires=['requests', 'six', 'py7zr', 'pyyaml'],
       extras_require={'dev': ['pytest', 'pytest-pep8', 'pytest-cov', 'flake8']},
       scripts=["bin/aqt"],
       classifiers=[