[segment] added kubecontext segement

Author: sandjaie

Diff for: powerline_shell/segments/kubecontext.py renamed to powerline_shell/segments/kube_context.py

@@ -9,7 +9,7 @@
 class Segment(BasicSegment):
     def add_to_powerline(self):
         kube_context = os.environ.get("KUBECONFIG")
-        if kubecontext:
+        if kube_context:
             self.powerline.append(" kctx:%s " % os.path.basename(kube_context),
                                   self.powerline.theme.KUBE_CONTEXT_FG,
                                   self.powerline.theme.KUBE_CONTEXT_BG)