Note `pod try ...` in readme

I encourage people to use `pod try`. It just works! :)

```sh
➜  ~  pod try TDBSplashscreen
Updating spec repositories

Trying TDBSplashscreen
Analyzing dependencies
Downloading dependencies
Using TDBSplashscreen (1.0.0)
Generating Pods project
Integrating client project
Opening '/private/tmp/CocoaPods/Try/TDBSplashscreen/Example/TDBSplashscreen.xcworkspace'
➜  ~
```