Add info about publishing reports on Azure (closes DevExpress#4250)

A little more explanation

.travis.yml

@@ -1,36 +1,19 @@
-if: NOT (commit_message =~ /^\[docs\]/ OR branch = 'new-docs')
-
-addons:
- chrome:  stable
- firefox: latest
- apt:
-  packages:
-   - dbus
-
 language: node_js
 matrix:
  include:
   - node_js: "8"
-    env: GULP_TASK="test-server"
-  - node_js: "stable"
-    env: GULP_TASK="test-server"
-  - node_js: "10"
-    env: GULP_TASK="test-client-travis"
-  - node_js: "10"
-    env: GULP_TASK="test-client-travis-mobile"
-  - node_js: "10"
-    env: GULP_TASK="test-functional-local-headless-chrome"
-  - node_js: "10"
-    env: GULP_TASK="test-functional-local-headless-firefox"
-  - node_js: "10"
-    env: GULP_TASK="test-functional-local-legacy"
+    env: GULP_TASK="test-docs-travis" JEKYLL_ENV="testing"
  fast_finish: true
 
-cache:
-  directories:
-    - $HOME/.npm
+before_install:
+   - rvm install 2.5.1
+   - curl -o- -L https://yarnpkg.com/install.sh | bash
+   - export PATH=$HOME/.yarn/bin:$PATH
+   - yarn install
+
+cache: yarn
 
-install: travis_retry npm install
+install: bundle install
 
 branches:
   except: