Remove support for centos 6.

Graphite 1.x requires at least python 2.7, it is available with SCL but
it's a lot of work to adapt all the init-scripts and Ansible tasks to
work with SCL. I will remove support considering that I guess that there
are not that many people using centos 6 that like to use this role.

If you are using centos 6 and like to install graphite with this role,
use the 2.0 release of this role. It works well and installs graphite
0.9.15.

.travis.yml

@@ -6,7 +6,7 @@ language: python
 
 env:
   global:
-    - CONTAINER_IMAGES="images:centos/6 images:centos/7 images:debian/jessie images:debian/stretch ubuntu:14.04 ubuntu:16.04"
+    - CONTAINER_IMAGES="images:centos/7 images:debian/jessie images:debian/stretch ubuntu:14.04 ubuntu:16.04"
   matrix:
 
     - ANSIBLE_VERSIONS="2.1.6" ANSIBLE_EXTRA_VARS_LIST="version=0.9.15"

meta/main.yml

@@ -8,7 +8,6 @@ galaxy_info:
   platforms:
     - name: EL
       versions:
-        - 6
         - 7
     # - name: Fedora
     #   versions:

tasks/RedHat.yml

@@ -19,27 +19,14 @@
     - sudo
     - libffi-devel
 
-- name: "Install Twisted 15.3.0 on 6.x (never versions req python 2.7)"
-  pip:
-    name: "Twisted==15.3.0"
-  when: ansible_distribution_major_version|int < 7
-
 - name: Install uwsgi with pip
   pip:
     name: uwsgi
 
-- name: Install carbon-cache init.d script
-  template:
-    src: redhat_carbon_service.j2
-    dest: /etc/init.d/carbon-cache
-  when: ansible_distribution_major_version|int < 7
-  notify: restart carbon-cache
-
 - name: Install systemd unit carbon-cache.service
   template:
     src: carbon_service_systemd.j2
     dest: /etc/systemd/system/carbon-cache.service
-  when: ansible_distribution_major_version|int >= 7
   register: ccunit
 
 - name: Reload systemd if unit file has changed
@@ -59,32 +46,13 @@
     dest: /etc/uwsgi_graphite.ini
   notify: restart uwsgi
 
-- name: Install uwsgi init.d script
-  template:
-    src: redhat_uwsgi_service.j2
-    dest: /etc/init.d/uwsgi
-  when: ansible_distribution_major_version|int < 7
-  notify: restart uwsgi
-
 - name: Install systemd unit uwsgi.service
   template:
     src: uwsgi_systemd.j2
     dest: /etc/systemd/system/uwsgi.service
-  when: ansible_distribution_major_version|int >= 7
   register: uwsgiunit
 
 - name: Reload systemd if unit file has changed
   shell: systemctl daemon-reload
   when: uwsgiunit|changed
   notify: restart uwsgi
-
-- name: Check the install scripts perms
-  file:
-    path: /etc/init.d/{{ item }}
-    mode: 0755
-    owner: root
-    group: root
-  when: ansible_distribution_major_version|int < 7
-  with_items:
-    - carbon-cache
-    - uwsgi