Updates analyzer to output to a file

File is specified by way of analyzer_output_path. I'm also changing
from a hard error if a target can't be found to a warning.

I'm also including a new set of tests. I forgot to svn add this last
time around.

BUG=109173
TEST=covered by tests
R=mark@chromium.org

Review URL: https://codereview.chromium.org/429243003

git-svn-id: http://gyp.googlecode.com/svn/trunk@1959 78cadc50-ecff-11dd-a971-7dbc132099af