Fix references to Apache license (#81)

Signed-off-by: Yuri Shkuro <[email protected]>

setup.py

@@ -8,13 +8,13 @@
     author_email='[email protected]',
     description='OpenTracing API for Python. See documentation at http://opentracing.io',
     long_description='\n'+open('README.rst').read(),
-    license='MIT',
+    license='Apache License 2.0',
     url='https://github.com/opentracing/opentracing-python',
     keywords=['opentracing'],
     classifiers=[
-        'Development Status :: 3 - Alpha',
+        'Development Status :: 5 - Production/Stable',
         'Intended Audience :: Developers',
-        'License :: OSI Approved :: MIT License',
+        'License :: OSI Approved :: Apache Software License',
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: Implementation :: PyPy',