Fix ansible version and ansible-lint version

Ansible 1.9 or greater is required.

.travis.yml

@@ -1,7 +1,8 @@
 language: python
 python: "2.7"
 install:
-  - pip install ansible ansible-lint
+  - pip install -r requirements.txt
+  - pip install -r test-requirements.txt
 script:
   - ansible-playbook --syntax-check -i hosts site.yml
   - ansible-lint site.yml

requirements.txt

@@ -1,2 +1 @@
-ansible==1.9.3
-nose
+ansible>=1.9.3,<2

test-requirements.txt

@@ -0,0 +1 @@
+ansible-lint>=2.3.9,<3