Add overview of upgrading steps. Also capitalize roundup.

Author: rouilj

doc/upgrading.txt

@@ -19,10 +19,29 @@ then you don't need to do anything. If you're upgrading from 0.5.6 to
 0.6.8 though, you'll need to check the "0.5 to 0.6" and "0.6.x to 0.6.3"
 steps.
 
+General steps:
+
+   1. Make note of your current Roundup version.
+   2. Take your Roundup installation offline (web, email,
+      cron scripts, roundup-admin etc.)
+   3. Backup your Roundup instance
+   4. Install a new version of Roundup
+   5. Make version specific changes as described below for
+      each version transition. If you are starting at 1.5.0
+      and installing to 2.3, you need to make the changes for **all**
+      versions starting at 1.5 and ending at 2.3. E.G.
+      1.5.0 -> 1.5.1, 1.5.1 -> 1.6.0, ..., 2.1.0 -> 2.2.0,
+      2.2.0 -> 2.3.0.
+   6. Run ``roundup-admin -i <tracker_home> migrate`` for
+      **all** your trackers. This will update the database if
+      it is required.
+   7. Bring your Roundup instance back online
+   8. Test
+
 **IMPORTANT** The v1.5.x releases of Roundup were the last to support
 Python v2.5 and v2.6.  Starting with the v1.6 releases of Roundup
 Python version 2.7 that is newer than 2.7.2 is required to run
-roundup.  Starting with Roundup version 2.0.0 we also support Python 3
+Roundup.  Starting with Roundup version 2.0.0 we also support Python 3
 versions newer than 3.4.
 
 Contents: