Sanitize package name in main.clj

I'm not sure if this is a recent thing or not, but with 0.2.0-SNAPSHOT, the app will fail at runtime if you put a hyphen in the package name:

> lein droid new android-test com.android-test :target-sdk 15

This is because the package name is being sanitized in AndroidManifest.xml, but not in main.clj, so they are inconsistent. If you have a better solution, feel free to reject this PR.