Clarify prereqs. Wiki just gets you in dev mode (#2209)

When I read this the first time, I didn't see anything on the given page telling me anything about crew. Finally I realized that although the instruction was in a separate paragraph, it didn't expect me to have already gotten in to dev mode.
This way of phrasing it should help people know what they're looking for on the wiki.

README.md

@@ -21,11 +21,10 @@ Chromebooks with Chrome OS run a Linux kernel. The only missing pieces to use th
 Prerequisites
 -------------
 
-You will need a Chromebook with developer mode enabled.
+You will need a Chromebook with developer mode enabled.  To do so, select your device on
+[the ChromiumOS Wiki](https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices) and follow the instructions listed there.
 
-On [the ChromiumOS Wiki](https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices) select your device and follow the instructions listed there.
-
-Please be aware of the fact that developer mode is insecure if not properly configured.
+Please be aware of the fact that developer mode is insecure if not properly configured. Setting a password as instructed in the VT-2 login screen is essential.
 
 Installation
 ------------