Changed periods to colons before code snippets

Referencing issue https://github.com/sequelize/sequelize/issues/2899. 

Many of the code snippets that should have had a colon instead had a period. Periods were appropriate for some code blocks (and I left those as periods), but the ones below should have colons:

docs/articles/getting-started.md

@@ -40,7 +40,7 @@ $ npm install --save mariasql # for mariasql
 
 ## Connecting to the database
 
-Open the created directory in your favorite text editor and add a new file called `app.js` with the following content.
+Open the created directory in your favorite text editor and add a new file called `app.js` with the following content:
 
 ```js
 var Sequelize = require('sequelize')
@@ -83,7 +83,7 @@ This will define a user model that has a username and password. Furthermore, Seq
 
 ### Synchronizing the schema
 
-As we want to store data in the database, we need to create a representation of the model.
+As we want to store data in the database, we need to create a representation of the model:
 
 ```js    
 sequelize
@@ -107,7 +107,7 @@ Please note, that `{ force: true }` will drop the `Users` table and re-create it
 
 ### Configuration
 
-You might not need the timestamps or you might not want the plural of the model's name as table name, right? Luckily there are configuration possibilities for that.
+You might not need the timestamps or you might not want the plural of the model's name as table name, right? Luckily there are configuration possibilities for that:
     
 ```js
 var User = sequelize.define('User', {
@@ -352,7 +352,7 @@ return sequelize.Promise.all([
 
 ## A combined example
 
-Now that you know the basics of Sequelize, you might want to see everything in a single program.
+Now that you know the basics of Sequelize, you might want to see everything in a single program:
     
 ```js
 var Sequelize = require('sequelize')
@@ -387,4 +387,4 @@ As there are some more advanced features in Sequelize which are a bit inappropri
 [2]: /docs/latest/models#configuration
 [3]: /docs/latest/models#validations
 [4]: /docs/latest/models#finders
-[5]: /docs/latest/associations
\ No newline at end of file
+[5]: /docs/latest/associations