Use test_requirements.txt for dependencies

Author: bridadan

setup.py

@@ -57,12 +57,7 @@ def read(fname):
         "six>=1.0,<2.0",
         "colorama>=0.3,<0.5",
     ],
-    tests_require=[
-        "coverage>=4,<5",
-        "coveralls>=1,<2",
-        "mock>=2,<4",
-        "pytest>=3,<5",
-    ],
+    tests_require=read("test_requirements.txt").splitlines(),
     extras_require={
         "pyocd": ["pyocd==0.14.0"]
     },