Travis CI: Use the `bionic` distribution

.travis.yml

@@ -1,16 +1,16 @@
-language: generic
+dist: bionic
+language: python
 
-addons:
+python:
-  apt:
+  - 3.7.1
-    packages:
-    - luarocks
 
 install:
-  - pyenv global 3.6.3
+  - sudo apt-get update -qq
-  - pip3 install --user pre-commit
+  - sudo apt-get install -qqq luarocks
+  - pip3 install pre-commit
   - luarocks install --local luacheck
 
 script:
   # All linters are run with pre-commit hooks
   - export PATH="$HOME/.luarocks/bin:$PATH"
-  - $HOME/.local/bin/pre-commit run --all-files
+  - pre-commit run --all-files