ci: remove travis support

we use github actions now

.travis.yml

-os:
-  - linux
-
-language: go
-
-go:
-  - 1.12.x
-
-env:
-  global:
-    - GOTFLAGS="-race"
-  matrix:
-    - BUILD_DEPTYPE=gomod
-
-
-# disable travis install
-install:
-  - true
-
-script:
-  - bash <(curl -s https://raw.githubusercontent.com/ipfs/ci-helpers/master/travis-ci/run-standard-tests.sh)
-
-
-cache:
-  directories:
-    - $GOPATH/pkg/mod
-    - $HOME/.cache/go-build
-
-notifications:
-  email: false

README.md

@@ -5,7 +5,6 @@ go-car (go!)
 [![](https://img.shields.io/badge/project-ipld-orange.svg?style=flat-square)](https://github.com/ipld/ipld)
 [![](https://img.shields.io/badge/freenode-%23ipld-orange.svg?style=flat-square)](https://webchat.freenode.net/?channels=%23ipld)
 [![Coverage Status](https://codecov.io/gh/ipld/go-car/branch/master/graph/badge.svg)](https://codecov.io/gh/ipld/go-car/branch/master)
-[![Travis CI](https://travis-ci.org/ipld/go-car.svg?branch=master)](https://travis-ci.org/ipld/go-car)
 
 > go-car is a simple way of packing a merkledag into a single file