Flexible Dependencies for Development

In addition to pinning dependencies in *master*, it might make sense to keep the *develop* branch nice and flexible, with the expectation that it might break.

I think it makes sense to retain the capability to build from "unpublished" source when necessary.

As a rule-of-thumb, maybe we also agree that the minimum version accepted by *develop* be the version we pin in *master*.

setup.py

@@ -59,23 +59,28 @@
 
     install_requires=[
         'requests>=2.18.4',
-        'sslyze>=1.1.0',
+        'sslyze>=1.2.0',
         'wget>=3.2',
-        'docopt',
-        'pytablereader',
-        'pytablewriter',
-        'publicsuffix',
-        'pyopenssl>=17.2.0'
+        'docopt>=0.6.2',
+        'pytablereader>=0.15.0',
+        'pytablewriter>=0.27.1',
+        'publicsuffix>=1.1.0',
+        'pyopenssl>=17.4.0'
     ],
 
     extras_require={
         # 'dev': ['check-manifest'],
         'test': [
-            'tox',
-            'pytest'
+            'tox>=2.9.1',
+            'pytest>=3.3.0'
         ],
     },
 
+    # For linking to "unpublished" dependencies... When necessary.
+    # dependency_links=[
+    #     'git+https://github.com/nabla-c0d3/sslyze.git#egg=sslyze-1.2.1'
+    #  ],
+
     # Conveniently allows one to run the CLI tool as `pshtt`
     entry_points={
         'console_scripts': [