Update README.md

Author: fennifith

README.md

@@ -18,10 +18,21 @@ For demonstration and experimentation, an apk of the sample project can be downl
 
 The Gradle dependency is available through jCenter, which is used by default in Android Studio. To add the dependency to your project, copy this line into the dependencies section of your app's build.gradle file.
 
+##### AndroidX
+
+The Android support libraries are being refactored from `android.support.*` to `androidx.*` as detailed [here](https://developer.android.com/topic/libraries/support-library/androidx-overview). Until the refactored libraries reach version `1.0.0` (as of the time of writing the latest verison is `1.0.0-rc02`), two versions of Attribouter will be released - one for AndroidX, and one for old support libraries.
+ 
 ```gradle
 implementation 'me.jfenn:attribouter:0.1.3'
 ```
 
+##### Old Support Libraries
+
+```gradle
+implementation 'me.jfenn:attribouter:0.1.2'
+```
+
+
 #### Starting an Activity
 This is pretty simple.
 
@@ -45,3 +56,7 @@ This library does not use an auth key for the GitHub API by default. It does cac
 By default, Attribouter will use the configuration file at [res/xml/attribouter.xml](./attribouter/src/main/res/xml/attribouter.xml). You can either name your configuration file "attribouter.xml" to override the resource, or name it differently and call `.withFile(R.xml.[name])` on your instance of `Attribouter` instead.
 
 The configuration file consists of a single root element, `<about>`, with many child elements that can be placed any amount of times in any order, the same as views in a layout file. These elements, called "wedges" in this library for no apparent reason, are created by Attribouter and added to the page in the order and heirarchy that they are defined in. To create your configuration file, you can either use the [file from the sample project](./app/src/main/res/xml/about.xml) as a template or use [the documentation](https://jfenn.me/Attribouter/) to write your own.
+
+### Proguard
+
+This library uses GSON, which does not behave nicely with proguard as it uses reflection to instantiate classes and initialize variables based on their names. It is recommended to use the [example configuration](https://github.com/google/gson/blob/master/examples/android-proguard-example/proguard.cfg) in GSON's repo to prevent these issues.