Fixed the broken getting-started link. (react-navigation#281)

* Fixed the broken getting-started link.

* Update API Reference URL

* Removed the absolute urls from both.

Author: mdchristians

website/i18n/en.json

@@ -148,7 +148,7 @@
     "Stay up to date|no description given": "Stay up to date",
     "Need help?|no description given": "Need help?",
     "This project is maintained by a dedicated group of people.|statement made to reader": "This project is maintained by a dedicated group of people.",
-    "Learn more using the [documentation on this site](getting-started.html) and [reading the API reference](/content/docs/api-reference.html).|no description given": "Learn more using the [documentation on this site](getting-started.html) and [reading the API reference](/content/docs/api-reference.html).",
+    "Learn more using the [documentation on this site](/docs/en/getting-started.html) and [reading the API reference](/docs/en/api-reference.html).|no description given": "Learn more using the [documentation on this site](getting-started.html) and [reading the API reference](/content/docs/api-reference.html).",
     "Browse Docs and API|no description given": "Browse Docs and API",
     "Ask questions about the documentation and project in the `#react-navigation` channel on the [Reactiflux Discord](https://discord.gg/4xEK3nD).|no description given": "Ask questions about the documentation and project in the `#react-navigation` channel on the [Reactiflux Discord](https://discord.gg/4xEK3nD).",
     "Read the release notes for new versions of React Navigation in the [releases tab on the Github repository](https://github.com/react-navigation/react-navigation/releases).|no description given": "Read the release notes for new versions of React Navigation in the [releases tab on the Github repository](https://github.com/react-navigation/react-navigation/releases).",

website/pages/en/help.js

@@ -19,7 +19,7 @@ class Help extends React.Component {
     const supportLinks = [
       {
         content:
-          <translate>Learn more using the [documentation on this site](getting-started.html) and [reading the API reference](/content/docs/api-reference.html).</translate>,
+          <translate>Learn more using the [documentation on this site](/docs/en/getting-started.html) and [reading the API reference](/docs/en/api-reference.html).</translate>,
         title: <translate>Browse Docs and API</translate>,
       },
       {