Android - UI rendering problems when using getbase.floatingactionbutton library

Question

I am having problems when using the library getbase.floatingactionbutton found here.

I am receiving the error: The following classes could not be instantiated:

• com.getbase.floatingactionbutton.FloatingActionMenu
• com.getbase.floatingactionbutton.FloatingActionButton

I have put

dependencies {
    compile 'com.getbase:floatingactionbutton:1.10.1'
}

into my app level build.gradle and have even taken the xml code for the fab straight from the sample app on github so what am I doing wrong? I'm at an end with this and I just can't figure it out!

xml:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:fab="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MapsActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <!-- other content in the activity -->

        <fragment xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/map"

            android:name="com.google.android.gms.maps.SupportMapFragment" />

    </LinearLayout>

    <FrameLayout
        android:id="@+id/frame_layout"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <!--  floating action menu with buttons -->

        <com.getbase.floatingactionbutton.FloatingActionsMenu
            android:id="@+id/right_labels"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true"
            android:layout_marginLeft="16dp"
            android:layout_marginStart="16dp"
            fab:fab_addButtonColorNormal="@color/white"
            fab:fab_addButtonColorPressed="@color/secondary_text"
            fab:fab_addButtonPlusIconColor="@color/accent_dark"
            fab:fab_addButtonSize="mini"
            fab:fab_labelStyle="@style/menu_labels_style"
            fab:fab_labelsPosition="right"
            android:layout_gravity="right|bottom">

            <com.getbase.floatingactionbutton.FloatingActionButton
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                fab:fab_colorNormal="@color/white"
                fab:fab_title="Label on the right"
                fab:fab_colorPressed="@color/secondary_text"/>

            <com.getbase.floatingactionbutton.FloatingActionButton
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                fab:fab_colorNormal="@color/white"
                fab:fab_size="mini"
                fab:fab_title="Another one on the right"
                fab:fab_colorPressed="@color/secondary_text"/>

        </com.getbase.floatingactionbutton.FloatingActionsMenu>

    </FrameLayout>
</FrameLayout>