setup.py: Add install_requires to avocado

Use setuptools's option install_requires, to signal
the dependencies avocado requires for full functionality.
Important for publishing avocado in PyPi [1].

[1] https://pypi.python.org/pypiSigned-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

setup.py

@@ -16,7 +16,11 @@
 import glob
 import os
 # pylint: disable=E0611
-from distutils.core import setup
+
+try:
+    from setuptools import setup
+except ImportError:
+    from distutils.core import setup
 
 import avocado.version
 
@@ -71,6 +75,16 @@ def _get_plugin_resource_files(path):
     return flist
 
 
+def get_requirements():
+    requirements = []
+    with open('requirements.txt', 'r') as req:
+        req_contents = req.read()
+        for line in req_contents.splitlines():
+            if not line.startswith("#"):
+                line = line.split("#")[0].strip()
+                requirements.append("%s" % line)
+    return requirements
+
 setup(name='avocado',
       version=avocado.version.VERSION,
       description='Avocado Test Framework',
@@ -86,4 +100,5 @@ setup(name='avocado',
                 'avocado.plugins'],
       package_data={'avocado.plugins': _get_plugin_resource_files('avocado/plugins/resources')},
       data_files=get_data_files(),
-      scripts=['scripts/avocado'])
+      scripts=['scripts/avocado'],
+      install_requires=get_requirements())