Check for negative/zero input in createBitmap()

Adds a check for negative or zero values for Width/Height in
ShadowBitmap.createBitmap(int width, int height, Bitmap.Config config)
implementation. Raises IllegalArgumentException if params are negative
or zero. Follows implementation in android.graphics.bitmap.
Merge pull request #1216 from Graya3000/master

Check for negative/zero input in createBitmap()
Preserve stack map frames.
Merge pull request #1217 from cushon/master

Preserve stack map frames.
Compile with JDK 7 (default) and 8.
Merge pull request #1218 from robolectric/jw/jdk8

Compile with JDK 7 (default) and 8.