Add Jenkinsfile for build testing.

Jenkinsfile

@@ -0,0 +1,42 @@
+pipeline {
+  agent any
+  stages {
+    stage('Deps') {
+      steps {
+        sh '''mix deps.get
+mix deps.compile'''
+      }
+    }
+    stage('Build') {
+      steps {
+        sh 'mix compile'
+      }
+    }
+    stage('Database') {
+      steps {
+        sh '''mix ecto.create
+mix ecto.migrate'''
+      }
+    }
+    stage('Test') {
+      steps {
+        sh '''mix test --cover
+'''
+      }
+    }
+    stage('Pre-Deploy') {
+      parallel {
+        stage('Webpack') {
+          steps {
+            sh 'mix phx.digest'
+          }
+        }
+        stage('JUnit') {
+          steps {
+            junit 'reports/*.xml'
+          }
+        }
+      }
+    }
+  }
+}