Update README.md

Add more social apis, related to: issue #58

README.md

@@ -136,6 +136,10 @@ A collective list of JSON APIs for use in web development.
 | API | Description | OAuth |Link |
 |---|---|---|---|
 | Full Contact | Get Social Media profiles and contact Information | Yes | [Go!](https://www.fullcontact.com/developer/docs/) |
+| LinkedIn REST-API | The foundation of all digital integrations with LinkedIn | Yes | [Go!](https://developer.linkedin.com/docs/rest-api) |
+| Facebook API | Facebook Login, Share on FB, Social Plugins, Analytics and more | Yes | [Go!](https://www.fullcontact.com/developer/docs/) |
+| Twitter API | Read and write Twitter dat | Yes | [Go!](https://dev.twitter.com/rest/public) |
+
 
 ### Security