API improvements

[bradroid]

Hello, thanks for the nice library I have one comment.

I needed to specify the size of the dots, I needed all the dots to be the same size.

I wasn't sure which number (1-6) to use, so I used all of them:

    <com.chahinem.pageindicator.PageIndicator
        app:piSize1="10dp"
        app:piSize2="10dp"
        app:piSize3="10dp"
        app:piSize4="10dp"
        app:piSize5="10dp"
        app:piSize6="10dp"/>

This works, but I think that the you could improve your API to make it doable with 1 property/method, since this seems (to me, i might be wrong) like the most common use case.