Update CI configurations

.appveyor.yml

@@ -18,7 +18,7 @@ install:
   - "python -m pip install --disable-pip-version-check --user --upgrade pip"
   - "python -m pip install --disable-pip-version-check --user --upgrade pip"
 
 
   # Installing Poetry
   # Installing Poetry
-  - "python -m pip install poetry --pre -U"
+  - "python get-poetry.py --preview -y"
 
 
   # Install dependencies
   # Install dependencies
   - "poetry install -v"
   - "poetry install -v"

.travis.yml

@@ -12,7 +12,8 @@ cache:
 
 
 install:
 install:
   - pip install pip -U
   - pip install pip -U
-  - pip install poetry --pre -U
+  - python get-poetry.py --preview -y
+  - source $HOME/.poetry/env
   - poetry install -v
   - poetry install -v
 
 
 script: pytest -q tests/
 script: pytest -q tests/
@@ -22,6 +23,9 @@ jobs:
   - python: '2.7'
   - python: '2.7'
   - python: '3.5'
   - python: '3.5'
   - python: '3.6'
   - python: '3.6'
+  - python: '3.7'
+    dist: xenial
+    sudo: true
   - stage: linting
   - stage: linting
     python: '3.6'
     python: '3.6'
     install:
     install: