[NaCl SDK] Add getting_started/README and getting_started/part2/README.

These were checked in, but not copied to the SDK build directory.

BUG=none
R=sbc@chromium.org

Review URL: https://codereview.chromium.org/25887004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226845 0039d316-1c4b-4281-b951-d872f2087c98
[NaCl SDK] Add test for url_loader example.

BUG=none
R=sbc@chromium.org

Review URL: https://codereview.chromium.org/23461007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226846 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226846