Remove .travis.yml because we're switching to CircleCI

.travis.yml

@@ -1,22 +0,0 @@
-language: python
-dist: trusty
-sudo: required
-python:
-  - "3.6"
-  - "3.6-dev"
-  - "3.7-dev"
-  - "nightly"
-# command to install dependencies
-install:
-  - sudo apt-get update && sudo apt-get install python3-pyqt5
-  - pip install -r install/requirements.txt
-  - pip install -r install/requirements-tests.txt
-  - pip install pytest-cov flake8
-before_script:
-    # stop the build if there are Python syntax errors or undefined names
-    - flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics
-    # exit-zero treats all errors as warnings.  The GitHub editor is 127 chars wide
-    - flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
-# run CLI tests and local GUI tests
-script:
-  - xvfb-run pytest --cov=onionshare --cov=onionshare_gui -vvv tests/