Update README.md

Author: escherba

README.md

@@ -7,7 +7,7 @@ fast non-cryptographic hash function.
 [![Latest
 Version](https://img.shields.io/pypi/v/metrohash.svg)](https://pypi.python.org/pypi/metrohash)
 [![Downloads](https://img.shields.io/pypi/dm/metrohash.svg)](https://pypistats.org/packages/metrohash)
-[![License](https://img.shields.io/pypi/l/metrohash.svg)](https://pypi.python.org/pypi/metrohash)
+[![License](https://img.shields.io/pypi/l/metrohash.svg)](https://opensource.org/licenses/Apache-2.0)
 [![Supported Python
 versions](https://img.shields.io/pypi/pyversions/metrohash.svg)](https://pypi.python.org/pypi/metrohash)