Remove .travis.yml, we use another CI/CD pipelines

.travis.yml

-language: cpp
-sudo: required
-dist: trusty
-
-before_install:
-  - sudo add-apt-repository -y ppa:beineri/opt-qt57-trusty
-  - sudo apt-get update -qq
-
-install:
-  - sudo apt-get -y install build-essential fuse zsync desktop-file-utils
-  - sudo apt-get -y install qt57base qt57svg qt57declarative qt57quickcontrols
-  # Replace linuxdeployqt download URL to official download URL when the stable version released
-  - curl -L -o linuxdeployqt https://dl.dropboxusercontent.com/u/150776/temp/linuxdeployqt-799f704-x86-64.appimage
-  - sudo install -m 755 -p linuxdeployqt /usr/local/bin/linuxdeployqt
-  - rm linuxdeployqt
-
-before_script:
-  - sudo modprobe fuse
-  - source /opt/qt57/bin/qt57-env.sh
-
-script:
-  - sh ./pkg/build.sh appimage
-
-after_script:
-  - appimage_file="$(ls ./pkg/build/*.AppImage)"
-  - [ -f "${appimage_file}" ] && curl -T "${appimage_file}" "https://transfer.sh/${appimage_file}"