added requirements.txt file

Author: manfred-kaiser

requirements.txt

@@ -0,0 +1 @@
+ply

setup.py

@@ -8,6 +8,9 @@
 with open(path.join(this_directory, 'README.rst'), encoding='utf-8') as f:
     long_description = f.read()
 
+with open('requirements.txt') as f:
+    requirements = f.read().splitlines()
+
 setup(
     name="sifter",
     version="0.2.0",
@@ -22,9 +25,7 @@
         'Tracker': 'https://github.com/garyp/sifter/issues',
     },
     python_requires='>= 3.6',
-    install_requires=[
-        "ply",
-    ],
+    install_requires=requirements,
     classifiers=[
         "Programming Language :: Python",
         "Programming Language :: Python :: 3",