Remove travis (#1135)

Replaced by GitHub workflows.

.travis.yml

@@ -1,38 +0,0 @@
-language: cpp
-compiler:
-  - gcc
-before_script:
-  - |-
-    set -o errexit
-
-    sudo apt-get update
-    sudo apt-get install -y \
-      build-essential \
-      cmake \
-      git-core \
-      libboost-all-dev \
-      libglew-dev \
-      liblua5.1-0-dev \
-      libncurses5-dev \
-      libopenal-dev \
-      libssl-dev \
-      libvorbis-dev \
-      mercurial \
-      zlib1g-dev
-
-    hg clone -r stable-3.0 http://hg.icculus.org/icculus/physfs/
-    mkdir -p physfs/build
-    pushd physfs/build
-    cmake ..
-    make -j$(nproc)
-    sudo make install
-    popd
-script: |
-  cmake . -DCMAKE_BUILD_TYPE=Release
-  make -j$(nproc)
-notifications:
-  irc:
-    channels:
-      - "irc.freenode.org#otclient"
-    on_success: change
-    skip_join: true

README.md

@@ -1,4 +1,4 @@
-[![Build Status](https://secure.travis-ci.org/edubart/otclient.svg?branch=master)](http://travis-ci.org/edubart/otclient) [![Join the chat at https://gitter.im/edubart/otclient](https://img.shields.io/badge/GITTER-join%20chat-green.svg)](https://gitter.im/edubart/otclient?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Open Source Helpers](https://www.codetriage.com/edubart/otclient/badges/users.svg)](https://www.codetriage.com/edubart/otclient)
+[![Build Status](https://github.com/edubart/otclient/actions/workflows/build-vcpkg.yml/badge.svg)](https://github.com/edubart/otclient/actions/workflows/build-vcpkg.yml) [![Join the chat at https://gitter.im/edubart/otclient](https://img.shields.io/badge/GITTER-join%20chat-green.svg)](https://gitter.im/edubart/otclient?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Open Source Helpers](https://www.codetriage.com/edubart/otclient/badges/users.svg)](https://www.codetriage.com/edubart/otclient)
 
 ### What is otclient?