TBR docs: tweak syncbase overview background, add brew install

Change-Id: I38f3adb999312008805cd9fcaf3f568db8c481e6
diff --git a/concepts/syncbase-overview.md b/concepts/syncbase-overview.md
index 2f4ad18..6036b7e 100644
--- a/concepts/syncbase-overview.md
+++ b/concepts/syncbase-overview.md
@@ -33,17 +33,13 @@
 
 ## Background
 
-There are many storage systems that are trying to synchronize data across mobile
-devices. Those systems are mostly cloud-centric rather than peer-to-peer. If
-they are peer-to-peer, they are focused on files rather than structured storage.
-Few systems have the fine-grained access control or powerful conflict resolution
-we want. In summary, we're trying to solve a bunch of problems simultaneously
-whereas those other systems each solve a subset of those problems.
-
-- [Firebase](https://www.firebase.com/): Cloud-centric
-- [Parse](https://www.parse.com/): Cloud-centric
-- [Azure Mobile Services](https://azure.microsoft.com/en-us/documentation/articles/mobile-services-ios-get-started-offline-data/): Cloud-centric
-- [Bittorrent Sync](https://www.getsync.com/): Files/blobs only
+There are many storage systems that synchronize data between mobile devices, but
+most such systems are cloud-centric rather than peer-to-peer, and the few that
+are peer-to-peer typically focus on files rather than structured storage. In
+addition, very few systems have the fine-grained access control or powerful,
+configurable conflict resolution we want. In summary, we're trying to solve a
+bunch of problems simultaneously whereas those other systems each solve a subset
+of those problems.
 
 ## Data Model
 
diff --git a/contributing/README.md b/contributing/README.md
index a3fe153..4cb1361 100644
--- a/contributing/README.md
+++ b/contributing/README.md
@@ -42,12 +42,18 @@
 
 ### Prerequisites
 
-If you are developing on Darwin (OS X), you need to have the Xcode command
-line tools installed. You can quickly install these in the terminal with:
+If you are developing on Darwin (OS X), you need to have the Xcode Command Line
+Tools package installed. You can install this package from a terminal with:
 
     # Mac-only prerequisite install
     xcode-select --install
 
+On Darwin (OS X), you'll also need the [Homebrew package manager][brew]
+installed. You can install it with:
+
+    # Mac-only prerequisite install
+    ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
+
 The instructions on this page assume that the following software is installed and in your `PATH`:
 
 * curl