Remove obsolete Travis CI config

This hasn't been relevant for years now.

Closes #43

.travis.yml

@@ -1,15 +0,0 @@
-language: python
-# command to install dependencies
-sudo: false
-install: 
-    - "pip install -r https://raw.githubusercontent.com/ProgVal/Limnoria/testing/requirements.txt"
-    - "pip install -r requirements.txt"
-# command to run tests
-script: sphinx-build -nW -b html -d _build/doctrees . _build/html
-# Flags used here, not in `make html`:
-#  -n   Run in nit-picky mode. Currently, this generates warnings for all missing references.
-#  -W   Turn warnings into errors. This means that the build stops at the first warning and sphinx-build exits with exit status 1.
-notifications:
-    email: false
-matrix:
-    fast_finish: true