fix dependency

setup.py

@@ -2,13 +2,13 @@
 
 setup(
     name='cql_kernel',
-    version='0.2.2',
+    version='0.2.3',
     packages=['cqlshlib_cql_kernel', 'cqlshlib_cql_kernel.test', 'cql_kernel'],
     url='https://github.com/slowenthal/cql_kernel',
     license='Apache',
     author='Steven Lowenthal & Apache Cassandra Developers',
     author_email='[email protected]',
-    install_requires = ['cassandra-driver>=2.7.2, <3.0'],
+    install_requires = ['cassandra-driver>=2.7.2,<3.0'],
     tests_require = ['jupyter_kernel_test','nose>=1.3.7'],
     description='CQL Kernel for Jupyter based on cqlsh'
 )