chore(travis): Remove TravisCI configs

.travis.yml

-sudo: required
-services:
-- docker
-language: c
-addons:
-  apt:
-    packages:
-    - libgmp-dev
-before_install: bash contrib/travis/before-install.sh
-script: stack test --no-terminal --install-ghc --copy-bins --no-docker
-cache:
-  directories:
-  - "$HOME/.stack"
-  - ".stack-work"
-after_success: bash contrib/travis/after-success.sh

contrib/travis/after-success.sh

-#!/bin/bash
-set -euo pipefail
-IFS=$'\n\t'
-
-cp "$(stack path --local-bin)/shift" dist/
-
-docker build -t shift .
-
-# If this is not a pull request, update the branch's docker tag.
-if [ $TRAVIS_PULL_REQUEST = 'false' ]; then
-  docker tag shift quay.io/etcinit/shift:${TRAVIS_BRANCH/\//-} \
-    && docker push quay.io/etcinit/shift:${TRAVIS_BRANCH/\//-};
-
-  # If this commit has a tag, use on the registry too.
-  if ! test -z $TRAVIS_TAG; then
-    docker tag shift quay.io/etcinit/shift:${TRAVIS_TAG} \
-      && docker push quay.io/etcinit/shift:${TRAVIS_TAG};
-
-    github-release create \
-      --user etcinit \
-      --repo shift \
-      --tag ${TRAVIS_TAG} \
-      --name ${TRAVIS_TAG} \
-      --description "."
-
-    github-release upload \
-      --user etcinit \
-      --repo shift \
-      --tag ${TRAVIS_TAG} \
-      --name "shift-linux-amd64" \
-      --file dist/shift
-  fi
-fi

contrib/travis/before-install.sh

-#!/bin/bash
-set -euo pipefail
-IFS=$'\n\t'
-
-mkdir -p ~/.local/bin
-
-export PATH=$HOME/.local/bin:$PATH
-
-curl -L https://www.stackage.org/stack/linux-x86_64 \
-  | tar xz --wildcards --strip-components=1 -C ~/.local/bin '*/stack'
-curl -L https://github.com/aktau/github-release/releases/download/v0.6.2/linux-amd64-github-release.tar.bz2 | tar -xj --wildcards --strip-components=3 -C ~/.local/bin '*/github-release'
-
-stack setup
-stack install hscolour
-
-docker login -e="." -u="$DOCKER_USERNAME" -p="$DOCKER_PASSWORD" quay.io
-
-mkdir dist