Add startSpeaking to the Plugin and Example App

[esgraham]

Description

As an application developer, I'd like to use the startSpeaking method, in order to have the application speak the text given to the plugin.

As an user of the example application, I'd like to press the Start Talking button and have the application speak the text in the text box.

Acceptance Criteria

• [x] In the Android plugin code, within the CognitiveServices.java file, rename the SpeakText method to startSpeaking.
• [x] In the iOS plugin code, within the CDVCognitiveServices.h and CDVCognitiveServices.m files, rename the SpeakText method to startSpeaking.
• [x] In the plugin interface code, within the cognitiveservices.js file, rename the SpeakText method to startSpeaking.
• [x] In the Native code, all files under the cognitiveservices folder, rename the SpeakText method to startSpeaking.
• [x] In the Example app, add the startSpeaking functionality.
• [x] Update the Plugin README description and examples with the startSpeaking method.

Resources

The SDK uses the SpeakText method SpeechSynthesizer.SpeakText, so find and replace will not work.