Fixed README download link to get the correct GTest version

Summary: Signed-off-by: Nicholas Ormrod <njormrod@fb.com>

Test Plan: Clicked link, gtest started downloading

Reviewed By: markisaa@fb.com

Subscribers: sdwilsh, folly-diffs@, yfeldblum

FB internal diff: D1901849

Tasks: 6255850

Signature: t1:1901849:1426097071:e887ed8749c70d5e15877082ac0175ce3b56647e

README

@@ -16,7 +16,7 @@ Dependencies
 folly requires gcc 4.8+ and a version of boost compiled with C++11 support.
 
 Please download googletest from
-https://googletest.googlecode.com/files/gtest-1.6.0.zip and unzip it in the
+https://googletest.googlecode.com/files/gtest-1.7.0.zip and unzip it in the
 folly/test subdirectory.
 
 Ubuntu 13.10