be explitic with requires both in requirements.txt and setup.py

Author: tomato42

setup.py

@@ -22,7 +22,7 @@
       packages=["tlslite", "tlslite.utils", "tlslite.integration"],
       package_data={
                     'package1': ['LICENSE', 'README.md']},
-      install_requires=['ecdsa'],
+      install_requires=['ecdsa>=0.14'],
       obsoletes=["tlslite"],
       python_requires=">=2.6, !=3.0.*, !=3.1.*, !=3.2.*",
       classifiers=[