Updated build instructions & script.

Updated the README and the install-prereqs-ubuntu.sh script to reflect
changes in the PX4 build steps and the PX$ & NuttX repository used to
build ardupilot.

README.md

@@ -87,9 +87,8 @@ few minutes in Linux, OS X, or Windows.
  4. In the `ardupilot` directory, run `vagrant up` from the command
  line.  This will create a new Ubuntu Linux VM.
 
- 5. Run `vagrant ssh -c
- "ardupilot/Tools/scripts/install-prereqs-ubuntu.sh -y"`.  This will
- install all the prerequisites for doing ardupilot development.
+ 5. Run `vagrant ssh -c "ardupilot/Tools/scripts/install-prereqs-ubuntu.sh -y"`.
+ This will install all the prerequisites for doing ardupilot development.
 
 You can now run `vagrant ssh` to log in to the development
 environment.  The `~/ardupilot` directory in the VM is actually the
@@ -105,18 +104,11 @@ $ vagrant ssh
 # make configure
 ```
 
-Now edit `ardupilot/config.mk` so it has the following line:
-
-```
-PX4_ROOT = ~/PX4-Firmware
-```
-
 Back at the terminal:
 
 ```
-# cd ArduCopter
 # make px4
-# make px4-upload (optional)
+# make px4-upload  # (optional)
 ```
 
 # User Technical Support

Tools/scripts/install-prereqs-ubuntu.sh

@@ -5,7 +5,7 @@ BASE_PKGS="gawk make git arduino-core curl"
 SITL_PKGS="g++"
 PX4_PKGS="python-serial python-argparse openocd flex bison libncurses5-dev \
           autoconf texinfo build-essential libftdi-dev libtool zlib1g-dev \
-          genromfs"
+          zip genromfs"
 ASSUME_YES=false
 
 function maybe_prompt_user() {
@@ -42,8 +42,12 @@ fi
 $APT_GET update
 $APT_GET install $BASE_PKGS $SITL_PKGS $PX4_PKGS
 
-if [ ! -d ~/PX4-Firmware ]; then
-    git clone git://github.com/PX4/Firmware.git ~/PX4-Firmware
+if [ ! -d ../PX4-Firmware ]; then
+    git clone https://github.com/diydrones/PX4Firmware.git
+fi
+
+if [ ! -d ../PX4NuttX ]; then
+    git clone https://github.com/diydrones/PX4NuttX.git
 fi
 
 if [ ! -d ~/gcc-arm-none-eabi-4_6-2012q2 ]; then