update installation instructions to prefer rake install

Don't suggest standalone install via curl anymore because:

- hub may not be a single script in the near future
- `rake install` handles the Windows executable as well

README.md

@@ -31,27 +31,29 @@ Installing on OS X is easiest with Homebrew:
 $ brew install hub
 ~~~
 
-### Standalone
+### `rake install` from source
 
-`hub` is easily installed as a standalone script:
+This is the preferred installation method without when no package manager that
+supports hub is available:
 
 ~~~ sh
-$ curl http://hub.github.com/standalone -sLo ~/bin/hub &&
-  chmod +x ~/bin/hub
+# Download or clone the project from GitHub:
+$ git clone git://github.com/github/hub.git
+$ cd hub
+$ rake install
 ~~~
 
-Assuming "~/bin/" is in your `$PATH`, you're ready to roll:
+On a Unix-based OS, this installs under `PREFIX`, which is `/usr/local` by default.
+
+Now you should be ready to roll:
 
 ~~~ sh
 $ hub version
 git version 1.7.6
 hub version 1.8.3
 ~~~
 
-#### On Windows
-
-If you have mysysgit, open "Git Bash" and follow the steps above but put the
-`hub` executable in `/bin` instead of `~/bin`.
+#### Windows "Git Bash" (mysysgit) note
 
 Avoid aliasing hub as `git` due to the fact that mysysgit automatically
 configures your prompt to include git information, and you want to avoid slowing
@@ -78,16 +80,6 @@ $ hub hub standalone > ~/bin/hub && chmod +x ~/bin/hub
 This installs a standalone version which doesn't require RubyGems to
 run, so it's faster.
 
-### Source
-
-You can also install from source:
-
-~~~ sh
-$ git clone git://github.com/github/hub.git
-$ cd hub
-$ rake install prefix=/usr/local
-~~~
-
 ### Help! It's slow!
 
 #### Is `hub` noticeably slower than plain git?

Rakefile

@@ -104,7 +104,9 @@ end
 desc "Build standalone script"
 task :standalone => "hub"
 
-desc "Install standalone script and man pages if unix-based OS. If Windows, install executable and .bat file inside ruby/bin"
+desc %{Install standalone script and man page.
+On Unix-based OS, installs into PREFIX (default: `/usr/local`).
+On Windows, installs into Ruby's main bin directory.}
 task :install => "hub" do
   require 'rbconfig'
   if RbConfig::CONFIG['host_os'] =~ /mswin|mingw/