1. Update `ANDROID_SDK_ROOT` to `ANDROID_HOME`. The former variable is
deprecated. (see https://developer.android.com/tools/variables#envar)
2. Remove `ANDROID_NDK_HOME` environment variable. This should allow the
build script to work out of the box for more folks.
3. Check that Java is on the `PATH` as opposed to just installing it.
`asdf` and other runtime management tools are pretty popular, and all
we care about is that the Java version is accessible.
4. Remove calls to `sudo`. Check to see if CocoaPods exists, if it
doesn't install it using Homebrew which doesn't require `sudo`.
Added guilds for setting up a public bootstrap, a dev network,
and config templates for dev nodes. Added link in the contribution
guide to dev network setup guide.
