Change order of sections in INSTALL file, mention Homebrew

INSTALL.md

-Installing a binary distribution package
-========================================
+# Installing a binary distribution package
 
 No official binary distribution packages are provided by the gflags developers.
-There may, however, be binary packages available for your OS. Please consult
-also the package repositories of your Linux distribution.
+There may, however, be binary packages available for your operating system.
+Please consult also the package repositories of your Linux distribution.
 
-For example on Debian/Ubuntu Linux, gflags can be installed using the
-following command:
+On Debian/Ubuntu Linux, gflags can be installed using the following command:
 
     sudo apt-get install libgflags-dev
 
-Compiling the source code with vcpkg
-=========================
+On macOS, [Homebrew](https://brew.sh/) includes a formula for gflags:
+
+    brew install gflags
+
+
+# Compiling the source code with Bazel
+
+To use gflags in a [Bazel](http://bazel.io) project, map it in as an external
+dependency by editing your WORKSPACE file:
+
+    git_repository(
+        name = "com_github_gflags_gflags",
+        commit = "<INSERT COMMIT SHA HERE>",
+        remote = "https://github.com/gflags/gflags.git",
+    )
+
+You can then add `@com_github_gflags_gflags//:gflags` to the `deps` section of a
+`cc_binary` or `cc_library` rule, and `#include <gflags/gflags.h>` to include it
+in your source code.
+
+
+# Compiling the source code with vcpkg
 
 You can download and install gflags using the [vcpkg](https://github.com/Microsoft/vcpkg) dependency manager:
 
@@ -23,8 +41,8 @@ You can download and install gflags using the [vcpkg](https://github.com/Microso
 
 The gflags port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please [create an issue or pull request](https://github.com/Microsoft/vcpkg) on the vcpkg repository.
 
-Compiling the source code with CMake
-=========================
+
+# Compiling the source code with CMake
 
 The build system of gflags is since version 2.1 based on [CMake](http://cmake.org).
 The common steps to build, test, and install software are therefore:
@@ -77,19 +95,3 @@ GFLAGS_INTTYPES_FORMAT      | String identifying format of built-in integer type
 GFLAGS_INCLUDE_DIR          | Name of headers installation directory relative to CMAKE_INSTALL_PREFIX.
 LIBRARY_INSTALL_DIR         | Name of library installation directory relative to CMAKE_INSTALL_PREFIX.
 INSTALL_HEADERS             | Request installation of public header files.
-
-Using gflags with [Bazel](http://bazel.io)
-=========================
-
-To use gflags in a Bazel project, map it in as an external dependency by editing
-your WORKSPACE file:
-
-    git_repository(
-        name = "com_github_gflags_gflags",
-        commit = "<INSERT COMMIT SHA HERE>",
-        remote = "https://github.com/gflags/gflags.git",
-    )
-
-You can then add `@com_github_gflags_gflags//:gflags` to the `deps` section of a
-`cc_binary` or `cc_library` rule, and `#include <gflags/gflags.h>` to include it
-in your source code.