Make rails runner command options more obvious

We're surrounding the options in angle brackets `<>` as is convention in `curl`:

```
$ curl --help
Usage: curl [options...] <url>
```

And then in square brackets `[]` with bars `|` as in `tar`:

```
$ tar --help
...
Create: tar -c [options] [<file> | <dir> | @<archive> | -C <dir> ]
```

To further clarify that the command can be used with both, we now show examples:

```
Examples:
    rails runner 'puts Rails.env'
        This runs the code `puts Rails.env` after loading the app

    rails runner path/to/filename.rb
        This runs the Ruby file located at `path/to/filename.rb` after loading the app
```

This format was taken from the `find` man pages:

```
EXAMPLES
     The following examples are shown as given to the shell:

     find / \! -name "*.c" -print
             Print out a list of all the files whose names do not end in .c.

     find / -newer ttt -user wnj -print
             Print out a list of all the files owned by user ``wnj'' that are newer than the file ttt.
```

The the text at the bottom is also shifted to improve readability.

railties/lib/rails/commands/runner.rb

@@ -9,7 +9,7 @@ if ARGV.first.nil?
 end
 
 ARGV.clone.options do |opts|
-  opts.banner = "Usage: rails runner [options] ('Some.ruby(code)' or a filename)"
+  opts.banner = "Usage: rails runner [options] [<'Some.ruby(code)'> | <filename.rb>]"
 
   opts.separator ""
 
@@ -22,14 +22,23 @@ ARGV.clone.options do |opts|
   opts.on("-h", "--help",
           "Show this help message.") { $stdout.puts opts; exit }
 
+    opts.separator ""
+    opts.separator "Examples: "
+
+    opts.separator "    rails runner 'puts Rails.env'"
+    opts.separator "        This runs the code `puts Rails.env` after loading the app"
+    opts.separator ""
+    opts.separator "    rails runner path/to/filename.rb"
+    opts.separator "        This runs the Ruby file located at `path/to/filename.rb` after loading the app"
+
   if RbConfig::CONFIG['host_os'] !~ /mswin|mingw/
     opts.separator ""
     opts.separator "You can also use runner as a shebang line for your executables:"
-    opts.separator "-------------------------------------------------------------"
-    opts.separator "#!/usr/bin/env #{File.expand_path($0)} runner"
+    opts.separator "    -------------------------------------------------------------"
+    opts.separator "    #!/usr/bin/env #{File.expand_path($0)} runner"
     opts.separator ""
-    opts.separator "Product.all.each { |p| p.price *= 2 ; p.save! }"
-    opts.separator "-------------------------------------------------------------"
+    opts.separator "    Product.all.each { |p| p.price *= 2 ; p.save! }"
+    opts.separator "    -------------------------------------------------------------"
   end
 
   opts.order! { |o| code_or_file ||= o } rescue retry