[ci skip] Improve encrypted commands USAGE

This streamlines the lovely foundation Bogdan added. Mainly to add
guidance around encryption keys and remove some backticks.

Finally it adds some mention of how to access these files from Ruby
in apps.

[ Kasper Timm Hansen & bogdanvlviv ]

Author: kaspth

railties/lib/rails/commands/encrypted/USAGE

@@ -1,22 +1,28 @@
 === Storing Encrypted Files in Source Control
 
-The Rails `encrypted` commands provide access to encrypted files.
+The Rails `encrypted` commands provide access to encrypted files or configurations.
+See the `Rails.application.encrypted` documentation for using them in your app.
+
+=== Encryption Keys
+
+By default, Rails looks for the encryption key in `config/master.key` or
+`ENV["RAILS_MASTER_KEY"]`, but that lookup can be overriden with `--key`:
+
+   rails encrypted:edit config/encrypted_file.yml.enc --key config/encrypted_file.key
+
+Don't commit the key! Add it to your source control's ignore file. If you use
+Git, Rails handles this for you.
 
 === Editing Files
 
-`rails encrypted:edit config/encrypted_file.yml.enc` opens a temporary file
-in `$EDITOR` with the decrypted contents of `config/encrypted_file.yml.enc` to
-edit. The encrypted key is either stored in `config/master.key`
-or `ENV["RAILS_MASTER_KEY"]` is used, but you can provide relative path
-to the encryption key by using `--key` option:
+To edit or create an encrypted file use:
+
+   rails encrypted:edit config/encrypted_file.yml.enc
 
-`rails encrypted:edit config/encrypted_file.yml.enc --key config/encrypted_file.key`.
+This opens a temporary file in `$EDITOR` with the decrypted contents for editing.
 
-=== Viewing files
+=== Viewing Files
 
-`rails encrypted:show config/encrypted_file.yml.enc` prints the decrypted contents of
-`config/encrypted_file.yml.enc` file. The encrypted key is either stored in `config/master.key`
-or `ENV["RAILS_MASTER_KEY"]` is used, but you can provide relative path
-to the encryption key by using `--key` option:
+To print the decrypted contents of an encrypted file use:
 
-`rails encrypted:show config/encrypted_file.yml.enc --key config/encrypted_file.key`.
+   rails encrypted:show config/encrypted_file.yml.enc