Multi size support

[yuttadhammo]

Hey, thanks for the great widget; anumodana :)

Hope this is somehow helpful, here are the changes in brief:

• Upped targetSdk to 17 (this is recommended by the SDK)
• added supports-screens tag, which allows the WebView to show correctly on larger screens - I don't think there are any screen sizes this app shouldn't support...
• simplified main.xml layout - WebViews are already scrollable, so there shouldn't be need to put one in a ScrollView; also forced to fill screen
• added zoom controls & pinch-to-zoom capability (if present) to WebView - on tablets this is useful since the text is fairly small.

[kasparsj]

Great! I'll try to merge in soon.