Using the command line, in the root of your project, run :
./gradlew clean && ./gradlew build
Then recompile your project in studio and you should see your new dependencies.
EDIT: At the time of the answer, Android studio didn't propose the "Gradle sync" button. It now does, so rather than using the command line, you can hit the button, and it will basically run ./gradlew clean && ./gradlew build
for you.
Anyway, it's always good to know how to do it in command line :)
The name of the button is: Sync Project with Gradle Files
See the screenshot below.
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