fix pyside dependency

setup.py

@@ -30,13 +30,12 @@ setup(
             'mseedpeek=mseedpeek.mseedpeek:main',
         ],
     },
-    install_requires=['pyside2'],
+    install_requires=['PySide2'],
     setup_requires=[],
     extras_require={
         'dev': [
             'flake8',
             'tox',
-            'pyside2',
         ]
     },
     license="GNU General Public License v3",