setuptools is erroneously declared as a runtime dependency
The code base does not appear to use `setuptools` nor `pkg_resources`:

```
…\\kubernetes-client-python
❯ rg -M 150 "pkg_resources"

…\\kubernetes-client-python
❯ rg -M 150 "setuptools"
setup.py
15:from setuptools import setup
27:# prerequisite: setuptools
28:# http://pypi.python.org/pypi/setuptools

requirements.txt
4:setuptools>=21.0.0  # PSF/ZPL

kubernetes\\README.md
31:Install via [Setuptools](http://pypi.python.org/pypi/setuptools).
```
diff --git a/setup.py b/setup.py
index 04bc04cd3..49fae21d4 100644
--- a/setup.py
+++ b/setup.py
@@ -35,7 +35,9 @@ with open('requirements.txt') as f:
     for line in f:
         line, _, _ = line.partition('#')
         line = line.strip()
-        if ';' in line:
+        if not line or line.startswith('setuptools'):
+            continue
+        elif ';' in line:
             requirement, _, specifier = line.partition(';')
             for_specifier = EXTRAS.setdefault(':{}'.format(specifier), [])
             for_specifier.append(requirement)
['setup.py']