Don't install tests module

Fixes #153

Author: Hugo Osvaldo Barrera

setup.py

@@ -5,7 +5,7 @@
 
 setup(
     name="python-barcode",
-    packages=find_packages(),
+    packages=find_packages(exclude=["tests"]),
     url="https://github.com/WhyNotHugo/python-barcode",
     license="MIT",
     author="Hugo Osvaldo Barrera et al",