Remove release.py and Rakefile and also revamp CI

This project is centered around providing an Emacs Lisp major mode to the programming language
Elixir. It is a higher maintenance burden to demand Python and Ruby on the developer machine.

Also, this PR revamps the CI (which used the Rakefile) to use
https://github.com/purcell/nix-emacs-ci . This is a more recent approach to many Emacs versions on
Travis.

Author: Victor Oliveira Nascimento

.travis.yml

@@ -1,12 +1,11 @@
 language: elixir
 cache: apt
 env:
-  - EVM_EMACS=24.3 TEST_RUN="rake test"
-  - EVM_EMACS=24.4 TEST_RUN="rake test"
-  - EVM_EMACS=24.5 TEST_RUN="rake test-no-gui"
-  - EVM_EMACS=25.1 TEST_RUN="rake test"
-  - EVM_EMACS=25.2 TEST_RUN="rake test"
-  # - EVM_EMACS=git-snapshot TEST_RUN="rake test"
+  - EVM_EMACS=24.3
+  - EVM_EMACS=24.4
+  - EVM_EMACS=24.5
+  - EVM_EMACS=25.1
+  - EVM_EMACS=25.2
 matrix:
   include:
     - elixir: 1.0.5
@@ -22,4 +21,4 @@ before_install:
 install:
   - cask install
 script:
-  - $TEST_RUN
+  - cask exec ert-runner

CONTRIBUTING.md

@@ -16,8 +16,8 @@ should take to help get it added/fixed in emacs-elixir
     * elixir-mode
     * emacs
 
-  * Ideally, creating a pull request with a (failing) test case demonstrating
-    what's wrong. This makes it easy for us to reproduce & fix the problem.
+  * Ideally, creating a pull request with a test case demonstrating what's wrong.
+    This makes it easy for us to review, reproduce & fix the problem.
 
 You might also hop into the IRC channel (``#elixir-lang`` on ``irc.freenode.net``)
 & raise your question there, as there may be someone who can help you with a
@@ -58,14 +58,15 @@ substantial time for the all-volunteer team to get to.
 
 ## How to run tests
 
-There are three tools that helps us to test emacs-elixir:
+There are two tools that helps us to test emacs-elixir:
 
-* [EVM](https://github.com/rejeep/evm) - a command-line tool which allows you to easily install, manage, and work with multiple Emacs versions.
 * [Cask](https://github.com/cask/cask) - a project management tool for Emacs that helps automate the package development cycle.
 * [Ert-runner](https://github.com/rejeep/ert-runner.el) - a tool for Emacs projects tested using Ert.
 
 ### Emacs Version Manager
 
+Emacs has many versions and currently we support from version 24+. If you want to reproduce a bug/issue on a specific version of Emacs, there are some alternatives like EVM. Here is a setup for EVM. 
+
 To install [EVM](https://github.com/rejeep/evm), run:
 
 ```bash
@@ -94,7 +95,7 @@ Read more about [EVM](https://github.com/rejeep/evm).
 To install Cask, run:
 
 ```bash
-$ curl -fsSkL https://raw.github.com/cask/cask/master/go | python
+$ curl -fsSL https://raw.githubusercontent.com/cask/cask/master/go | python
 $ export PATH="~/.cask/bin:$PATH" # Add it to your .bashrc or analogue
 ```