Remove ancient travis configuration

.travis.yml

@@ -1,23 +0,0 @@
-language: python
-cache: pip
-dist: bionic
-python:
-  - "2.7_with_system_site_packages"
-  - "3.7"
-addons:
-  apt:
-    packages:
-      - build-essential
-      - libcap-dev
-      - python-qt4
-      - python-pyqt5
-      - tor
-      - xvfb
-install:
-  - pip install -r requirements.txt
-  - python setup.py install
-  - export PYTHONWARNINGS=all
-script:
-  - python checkdeps.py
-  - python src/bitmessagemain.py -t
-  - python -bm tests