make the deprecation notice in README.md more prominent?

[enh-google]

the first thing on the page should probably be the deprecation notice, and then just a link to the migration samples, with the rest only of historical interest now?

[enh-google]

i'm also curious whether development/samples/browseable/RenderScriptIntrinsic/src/com.example.android.renderscriptintrinsic/MainActivity.java in the main tree should just be removed in favor of the stuff here?