Updates analyzer to output to a file

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

Committed: https://code.google.com/p/gyp/source/detail?r=1959

[Mark Mentovai, 2014-07-30 17:01:56]

LGTM

[sky, 2014-07-30 20:27:22]

Updated to not trip over pylint warnings by no subclassing a test. I'm going to
land.

[sky, 2014-07-30 20:29:35]

Committed patchset #2 manually as r1959 (presubmit successful).

[Mark Mentovai, 2014-07-30 20:29:43]

LGTM