ReadMe file for generating API documentation (#260)

* readme

* readme updated

* folder named changed to docs

Author: arafay-folio3

docs/README.md

@@ -0,0 +1,11 @@
+# Generate API Documentation
+### Steps
+* Download [doxygen]( http://www.stack.nl/~dimitri/doxygen/download.html) and open it.
+* Move Doxygen.app to /Applications folder.
+* Open Doxygen from Launchpad.
+* Select **/Applications** folder in working directory.
+* Select SDK root directory in source code directory.
+* Select **objective-c-sdk/API Docs** in Destination Directory.
+* Navigate to **RUN** tab and press **Run doxygen**.
+* This will generate HTML documentation in **objective-c-sdk/API Docs** directory.
+* Browse **objective-c-sdk/API Docs/HTML/index.html** in browser.