Add new library required for build test using Junit4 in "How To Build Aerogear Android"

<dependency>
    <groupId>com.android.support.test</groupId>
    <artifactId>runner</artifactId>
    <version>0.3</version>
    <type>aar</type>
    <exclusions>
        <exclusion>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-core</artifactId>
        </exclusion>
        <exclusion>
            <groupId>junit</groupId>
            <artifactId>junit-dep</artifactId>
        </exclusion>
    </exclusions>
</dependency>

<dependency>
    <groupId>com.android.support.test</groupId>
    <artifactId>rules</artifactId>
    <version>0.3</version>
    <type>aar</type>
</dependency>