Improve install documentation.

Author: mikaelpatel

build/INSTALL.txt

@@ -23,12 +23,14 @@ INSTALL COSA CUSTOM BOARDS
 ==========================
 
 1. Download custom board support and install in sketchbook hardware
-   directory.
+   directory. The command line build assumes that they are installed
+   with 1.0.X directory structure (i.e. without the avr level).
 
 2. Add symbolic link in COSA_DIR/variants to custom board variants.
    Example for Cosa-CustomBoard template.
    $ ln -s $SKETCHBOOK/hardware/CustomBoard/variants/VENDOR $COSA_DIR/variants
 
-3. Verify that the custom board is now available.
+3. Verify that the custom board is now available. The following
+   commands will generate and print the list of boards.
    $ cd $COSA_DIR/build
    $ cosa boards

doc/02-install.md

@@ -13,13 +13,25 @@ https://raw.githubusercontent.com/mikaelpatel/Cosa/master/package_cosa_index.jso
 
 ## Via GIT
 
+For Arduino 1.0.X:
 ```shell
 cd <custom_path>/sketchbook
-mkdir hardware # Create the hardware folder if missing
+mkdir hardware
 cd hardware
 git clone https://github.com/mikaelpatel/Cosa.git
 ```
 
+For Arduino 1.5.x and higher an extra avr directory level is needed:
+```shell
+cd <custom_path>/sketchbook
+mkdir hardware
+cd hardware
+mkdir Cosa
+cd Cosa
+git clone https://github.com/mikaelpatel/Cosa.git
+mv Cosa avr
+```
+
 Then you can update the library by using:
 
 ```shell