Fix issue #2205. Let the parse method throw a NumberFormatException if text cannot be converted into a number, instead of returning 0.0.

Patch by: shanjian
Review by: rdayal

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@2211 8db76d5a-ed1c-0410-87a9-c151d255dfc7