ci(travis): adds awesome_bot for linting *.md files (#218)

Author: juancarlostong

.travis.yml

@@ -5,13 +5,24 @@ git:
 install:
   - eval "$(gimme)"
 stages:
+  - name: 'Lint markdown files'
   - 'Lint'
   - 'Unit test'
   - 'Benchmark test'
   - 'Integration tests'
   - 'Source clear'
 jobs:
   include:
+    - stage: 'Lint markdown files'
+      language: ruby
+      rvm: 2.4.1
+      os: linux
+      install: gem install awesome_bot
+      script:
+        - find . -type f -name '*.md' -exec awesome_bot {} \;
+      notifications:
+        email: false
+
     - stage: 'Lint'
       env: GIMME_GO_VERSION=1.12.x GIMME_OS=linux GIMME_ARCH=amd64
       script: