Bug fix for camera stretching artifacts on some Android devices

This is a one-liner that fixes #3317. 

On certain popular Android devices (the 2013 Nexus 7, in particular), it is necessary for the previewSize and the pictureSize to have the same aspect ratio. To fix openFrameworks we just needed to call setPictureSize in the same place we do setPreviewSize. This information and fix suggestion come from a Google Android developer, through their issue tracker. See: https://code.google.com/p/android/issues/detail?id=73316 

I have tested the patched version on the 2013 Nexus 7, HTC One M8, and HTC One M7.