Fix method -increaseRef on PhxSocket, add tests

[gskbyte]

This PR basically fixes the implementation of the method -increaseRef by effectively generating a different string every time it's called.

This PR also adds support for tests the following way:

• Improve Podfile to add an example application target and a testing target. This fixes the fact that the PhoenixClient.xcworkspace was empty, now it can be opened for the example project.
• Pods had to be updated for this, and given that the .gitignore doesn't omit the Pods directory, we have to include the changes relative to updating SocketRocket to a newer version (a version 0.3.x was never released, it jumps to the 0.4)
• Add a test for the fixed method. Further tests will come in future PRs.

The actual changes are in the files Classes/PhxSocket.m and Example/ChannelDemo/ChannelDemoTests/PhxSocketTests.m. Changes on all other files are provoked by changes on Example/ChannelDemo/Podfile and then executing pod install