ci: Remove Travis CI configuration

Travis is no longer free to use.

.travis.yml

@@ -1,13 +0,0 @@
-dist: xenial
-language: python
-python:
-  - "3.5"
-  - "3.6"
-  - "3.7"
-  - "3.8-dev"
-install:
-    - pip install .[tests]
-    - pip install coveralls
-script: pytest
-after_success:
-  - coveralls

README.rst

@@ -4,16 +4,8 @@ PySecretHandshake - Secret Handshake in Python
 ==============================================
 
 
-|build-status| |code-coverage|
-
-This module implements Secret Handshake as specified in Dominc Tarr's paper `"Designing a Secret Handshake: Authenticated
-Key Exchange as a Capability System" <http://dominictarr.github.io/secret-handshake-paper/shs.pdf>`_ (Dominic Tarr, 2015).
+This module implements Secret Handshake as specified in Dominc Tarr's paper `"Designing a Secret Handshake:
+Authenticated Key Exchange as a Capability System" <http://dominictarr.github.io/secret-handshake-paper/shs.pdf>`_
+(Dominic Tarr, 2015).
 
 **Please, don't use this package in production. The implementation hasn't yet been carefully checked.**
-
-.. |build-status| image:: https://travis-ci.org/pferreir/PySecretHandshake.svg?branch=master
-                   :alt: Travis Build Status
-                   :target: https://travis-ci.org/pferreir/PySecretHandshake
-.. |code-coverage| image:: https://coveralls.io/repos/github/pferreir/PySecretHandshake/badge.svg?branch=master
-                   :alt: Code Coverage
-                   :target: https://coveralls.io/github/pferreir/PySecretHandshake?branch=master