Update README to point to correct (new) document links.
Update README to point to correct (new) document links.

BUG=http://code.google.com/p/nativeclient/issues/detail?id=1371
TEST=Manual.  Install SDK, open README and verify that hte links to (new) docs
work properly.

Review URL: http://codereview.chromium.org/6392040

git-svn-id: e22621a84199d42b34715cdc089545aeedbbf23f@701 050acbb0-2703-11df-ab0a-9f3f633ae91d

sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk,sbc100/nativeclient-sdk