Fix travis (openmaptiles#245)

Move to the installed default docker version.

.travis.yml

@@ -1,19 +1,13 @@
 sudo: required
 
-dist: xenial
+dist: trusty
 
 language: bash
 
 services:
   - docker
 
 before_install:
-  - sudo sh -c 'echo "deb https://apt.dockerproject.org/repo ubuntu-xenial main" > /etc/apt/sources.list.d/docker.list'
-  - sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
-  - sudo apt-get clean
-  - sudo apt-get update
-  - sudo apt-key update
-  - sudo apt-get -qqy -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" install docker-engine=1.11.0-0~xenial
   - sudo rm -f /usr/local/bin/docker-compose
   - curl -L https://github.com/docker/compose/releases/download/1.7.1/docker-compose-`uname -s`-`uname -m` > docker-compose
   - chmod +x docker-compose

QUICKSTART.md

@@ -13,7 +13,7 @@
 * bash
 * git
 * make 
-* docker         >=1.11
+* docker         >=1.12.3
     * https://www.docker.com/products/overview
 * docker-compose >=1.7.1
     * https://docs.docker.com/compose/install/

README.md

@@ -62,7 +62,7 @@ Together the layers make up the OpenMapTiles tileset.
 
 To work on OpenMapTiles you need Docker and Python.
 
-- Install [Docker](https://docs.docker.com/engine/installation/). Minimum version is 1.11.0+.
+- Install [Docker](https://docs.docker.com/engine/installation/). Minimum version is 1.12.3+.
 - Install [Docker Compose](https://docs.docker.com/compose/install/). Minimum version is 1.7.1+.
 - Install [OpenMapTiles tools](https://github.com/openmaptiles/openmaptiles-tools) with `pip install openmaptiles-tools`
 

quickstart.sh

@@ -31,7 +31,7 @@ testdata=${osm_area}.osm.pbf
 
 ##  Min versions ...
 MIN_COMPOSE_VER=1.7.1
-MIN_DOCKER_VER=1.11.0
+MIN_DOCKER_VER=1.12.3
 STARTTIME=$(date +%s)
 STARTDATE=$(date +"%Y-%m-%dT%H:%M%z")
 githash=$( git rev-parse HEAD )