Updated travis cfg to only build packages on deployment. Updated test targets

Author: Pan

.travis.yml

@@ -6,6 +6,7 @@ sudo: required
 services:
   - docker
 python:
+  - 2.6
   - 2.7
   - 3.4
   - 3.5
@@ -25,6 +26,8 @@ script:
   - nosetests
   - flake8 ssh2
 jobs:
+  allow_failures:
+    - python: 2.6
   include:
     - stage: build_packages
       python: 3.6