Remove the ext subpackage.

import segpy.ext.numpy will no longer be supported. It just doesn't play nice with a lot of Python tooling.  In future it will be
import segpy_numpy

segpy/ext/__init__.py

@@ -1,20 +0,0 @@
-import pkg_resources
-
-loaded = set()
-
-
-def load_entry_points(name=None):
-    """Load extension packages into the segpy.ext namespace.
-
-    Any packages registered against the 'segpy.ext' entry-point group will be
-    installed dynamically into the segpy.ext namespace.
-    """
-    for entry_point in pkg_resources.iter_entry_points(group='segpy.ext', name=name):
-        package = entry_point.load()
-        if package not in loaded:
-            loaded.add(package)
-            __path__.extend(package.__path__)
-            package.load()
-
-
-load_entry_points()