update travis config

.travis.yml

@@ -1,6 +1,7 @@
 language: python
 sudo: false
 cache: pip
+dist: xenial
 git:
   depth: 100000
 addons:
@@ -22,23 +23,28 @@ matrix:
       env: TOXENV=py36
     - python: 3.6-dev
       env: TOXENV=py36
+    - python: 3.7
+      env: TOXENV=py37
     - python: 3.7-dev
       env: TOXENV=py37
+    - python: 3.8-dev
+      env: TOXENV=py38
     - python: nightly
-      env: TOXENV=py37
+      env: TOXENV=py38
     - python: pypy
       env: TOXENV=pypy
     - python: pypy3
       env: TOXENV=pypy3
-    - python: 2.7
+    - python: 3.7
       env: TOXENV=docs
     - python: 2.7
       env: TOXENV=flake8
-    - python: 3.6
+    - python: 3.7
       env: TOXENV=flake8
   allow_failures:
     - python: 3.6-dev
     - python: 3.7-dev
+    - python: 3.8-dev
     - python: nightly
     - python: pypy3
 before_install:
@@ -63,4 +69,4 @@ deploy:
       tags: true
       repo: python-escpos/python-escpos
       branch: master
-      condition: $TRAVIS_PYTHON_VERSION = "3.6"
+      condition: $TRAVIS_PYTHON_VERSION = "3.7"

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py27, py34, py35, docs, flake8
+envlist = py27, py34, py35, py36, py37, docs, flake8
 
 [testenv]
 deps = nose