Update build badge, remove Travis configuration

.travis.yml

@@ -1,21 +0,0 @@
-dist: xenial
-language: python
-python:
-  - "3.6"
-  - "3.7"
-  - "3.8"
-install:
-    - pip install -r requirements.txt
-    - pip install braintree coveralls mock mysqlclient reportlab apprise
-env:
-  - DB=sqlite
-  - DB=mysql
-  - DB=postgres
-services:
-  - mysql
-addons:
-  postgresql: "9.6"
-script:
-  - coverage run --omit=*/tests/* --source=hc manage.py test
-after_success: coveralls
-cache: pip

README.md

@@ -1,6 +1,6 @@
 # Healthchecks
 
-[![Build Status](https://travis-ci.org/healthchecks/healthchecks.svg?branch=master)](https://travis-ci.org/healthchecks/healthchecks)
+![Build Status](https://github.com/healthchecks/healthchecks/workflows/Django%20CI/badge.svg)
 [![Coverage Status](https://coveralls.io/repos/healthchecks/healthchecks/badge.svg?branch=master&service=github)](https://coveralls.io/github/healthchecks/healthchecks?branch=master)