Added support for comments in proguard.cfg file
android-plugin already takes care for main application package
Fix toString error

Scala 2.10 has some issues with call to toString method. This error
occurs quite often, but workaround is clean and simple (on proguard level).
See https://issues.scala-lang.org/browse/SI-5397 for details.
Fix accesses to class members by introspection

Even for empty project with Scala 2.10, Proguard says:

There were 9 accesses to class members by means of introspection.
You should consider explicitly keeping the mentioned class members
(using '-keep' or '-keepclassmembers').
Add descriptor classes for scala bug workaround

Proguard says to explicitly keep mentioned classes.
Keep descriptor classes from libgdx

Without those, behavious can be undefined, because classes that
are needed, need those. Those classes are enough to run default,
empty project created with this template (it removes all proguard
warnings that are present without this file).
Do not prefer Idea editor

I've seen forks of this project that only change editor from Idea to
other editor in the plugins.sbt file. I believe it's best to not include
default IDE, but to include in README file how to work with each popular
IDE that work with Scala. It will help centralize the effort to create one,
single standard project template, and thus better one. The list here is taken
from description of Scala on Typesafe homepage.
Merge pull request #17 from aginiewicz/ide

Do not prefer Idea editor
Merge pull request #16 from aginiewicz/proguard

Improve default proguard setup