Retrofit 2 example tutorial but GsonConverterFactory display error "Cannot resolve symbol"

EDIT

retrofit 2 is now stable. Use

compile 'com.squareup.retrofit2:retrofit:2.3.0'
compile 'com.squareup.retrofit2:converter-gson:2.3.0'

in your build.gradle dependency section

old answer

with Retrofit 2.0 you have to declare in your build.gradle the convert factory you want to use. Add

compile 'com.squareup.retrofit:converter-gson:2.0.0-beta2'

to your gradle and sync it again

From another article on that site

Retrofit 2 doesn’t ship with Gson by default. Before, you didn’t need to worry about any integrated converter and you could use Gson out of the box. This library change affects your app and you need to import a converter as a sibling package as well. We’ll touch the converter later within this post and show you how to config the Gson or any other response converter for your app.

Thus, add this to your build.gradle

dependencies {  
    compile 'com.squareup.retrofit:converter-gson:2.0.0-beta2'
}

The reason to such behavior in my case was typo in build.gradle dependency. After beta4 release I've updated from:

compile 'com.squareup.retrofit:converter-gson:2.0.0-beta2'

to

 compile 'com.squareup.retrofit:converter-gson:2.0.0-beta4'

and the right dependency was

compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4'

Also worth notice, that beta4 - retrofit won't work with beta2 - gson!