Remove custom install command with dependency_links

since stem 1.7.0 is released and there is no need for it anymore

tox.ini

@@ -9,8 +9,8 @@ python =
 
 [testenv]
 # install_command can be removed when --process-dependency-links is not
-# needed anymore, and this section uncommented
-install_command = pip install --process-dependency-links {opts} {packages}
+# needed anymore, and this section commented
+# install_command = pip install {opts} {packages}
 
 # test that it can be installed with custom commands and clean env
 [testenv:inst]
@@ -18,7 +18,7 @@ skip_install = True
 commands =
     # this will fail until --process-dependency-links is not needed
     # it needs to be commented since error code will be still 1
-    # - pip install .
+    - pip install .
 ignore_errors = True
 recreate = True
 
@@ -26,7 +26,7 @@ recreate = True
 skip_install = True
     # this will fail until --process-dependency-links is not needed
     # it needs to be commented since error code will be still 1
-# commands = python setup.py install
+commands = python setup.py install
 recreate = True
 
 [testenv:unit]