flutter doctor currently checks for the existence of the atom plugin and prints out the installed version:

[✓] Atom - a lightweight development environment for Flutter
    • flutter plugin version 0.2.5
    • dartlang plugin version 0.6.39

We should change this check to be optional; if atom is not installed, change to not print anything. If it is, the text can remain as is - the version info.

/cc @danrubel