GridLayout compatibility - ClassNotFoundException: Didn't find class "android.support.v7.widget.GridLayout"

I'm trying to use GridLayout in my Android 2.2 project, and after having installed the gridlayout_v7 project in my workspace, adding it to my projects Android Dependencies, adding a custom xmlns for its custom attributes, and embedding it in my xml layout as such:

<android.support.v7.widget.GridLayout
    android:layout_width="match_parent"
    android:layout_height="300dp"
    grid:columnCount="2"
    grid:rowCount="3" >

    <include
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        layout="@layout/quick_contact" />
    <include
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        layout="@layout/quick_contact" />
    <include
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        layout="@layout/quick_contact" />
    <include
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        layout="@layout/quick_contact" />
    <include
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        layout="@layout/quick_contact" />
    <include
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        layout="@layout/quick_contact" />
</android.support.v7.widget.GridLayout>

I started getting the following exception at runtime:

java.lang.ClassNotFoundException: Didn't find class 
"android.support.v7.widget.GridLayout" on path: DexPathList[[zip file 
"system/framework/android.test.runner.jar", zip file "data/app/<app package>.apk"], 
nativeLibraryDirectories=[data/app-lib/<app package>, /vendor/lib, /system/lib]]

I have tried cleaning and rebuilding, removing the library and adding it again but to no avail. Any ideas as to what may be causing this?