Adding integerValueForParameter to GTMURLBuilder.
Makes it symmetric with setIntegerValue.

DELTA=8  (8 added, 0 deleted, 0 changed)

git-svn-id: http://google-toolbox-for-mac.googlecode.com/svn/trunk@652 7dc7ac4e-7543-0410-b95c-c1676fc8e2a3