Correct some typos

docs/install.rst

@@ -42,10 +42,10 @@ to your sources. You can use the following commands:
 
 .. code-block:: console
 
-   cd /etc/apt/sources.list.d
-   echo "deb http://apt.dev.grnet.gr precise main" | \
+   $ cd /etc/apt/sources.list.d
+   $ echo "deb http://apt.dev.grnet.gr precise main" | \
    sudo tee -a  apt.dev.grnet.gr.list
-   echo "deb-src http://apt.dev.grnet.gr precise main" | \
+   $ echo "deb-src http://apt.dev.grnet.gr precise main" | \
    sudo tee -a apt.dev.grnet.gr.list
 
 You will also need to import the repo's GPG key. You can use the ``curl`` tool

docs/overview.rst

 Overview
 ^^^^^^^^
 
-snf-image-creator is a simple command-line tools for creating OS images. The
+snf-image-creator is a simple command-line tool for creating OS images. The
 original media from which the image is created, can be a block device or a
 regular file that represents a hard disk. Given a media file, snf-image-creator
 will create a snapshot for it and will run a number of system preparation

docs/usage.rst

@@ -157,7 +157,7 @@ Wizard mode
 When *snf-mkimage* runs in *wizard* mode, the user is just asked to provide the
 following basic information:
 
- * Name: A short name for image (ex. "Slackware")
+ * Name: A short name for the image (ex. "Slackware")
  * Description: An one-line description for the image (ex. "Slackware Linux 14.0 with KDE")
  * Account: An *~okeanos* account email
  * Token: A token corresponding to the account defined previously