minor: update readme for 26compat branch

Author: TylerBrock

README.md

@@ -1,17 +1,17 @@
-# MongoDB C++ Driver [![Build Status](http://img.shields.io/travis/mongodb/mongo-cxx-driver/legacy.svg)](https://travis-ci.org/mongodb/mongo-cxx-driver)
+# MongoDB C++ Driver [![Build Status](http://img.shields.io/travis/mongodb/mongo-cxx-driver/26compat.svg)](https://travis-ci.org/mongodb/mongo-cxx-driver)
 Welcome to the MongoDB C++ Driver!
 
 Use this branch if:
 
+ - You have existing code that used the driver from the server source
+ and want it to continue working without modification.
+
+Switch to the legacy branch if:
+
  - You are using MongoDB's C++ driver for the first time.
  - You had been using 26compat (or the driver inside of the server source) and
  want to benefit from incremental improvements but have the same overall API.
 
-Switch to the 26compat branch if:
-
- - You have existing code that used the driver from the server source
- and want it to continue working without modification.
-
 **Please Note:** As of MongoDB 2.6.0-rc1, it is no longer possible to build the
 driver from the server sources: this repository is the only approved source for
 driver builds.