cosa, install on mac; Cosa/OutputPin.hh: No such file or directory

Trying to follow the install instructions of Cosa. Not greatly successful:

:avr ehsmeng> pwd
/Users/ehsmeng/Documents/Arduino/hardware/Cosa/avr
:avr ehsmeng> ls
Doxyfile LICENSE.txt boards/ build/ doc/ libraries/ platform.txt variants/
INSTALL.txt README.md boards.txt cores/ examples/ mainpage.dox spec/
:avr ehsmeng>

Arduino: 1.6.1 (Mac OS X), Board: "Arduino Uno"

Build options changed, rebuilding all

/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/bin/avr-g++ -c -g -Os -w -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10601 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR -I/Applications/Arduino.app/Contents/Resources/Java/hardware/arduino/avr/cores/arduino -I/Applications/Arduino.app/Contents/Resources/Java/hardware/arduino/avr/variants/standard /var/folders/10/hkv8gs2j7lvfn_gzgh37jzzr0000gn/T/build7823328112842144068.tmp/CosaBlink.cpp -o /var/folders/10/hkv8gs2j7lvfn_gzgh37jzzr0000gn/T/build7823328112842144068.tmp/CosaBlink.cpp.o
CosaBlink.ino:30:29: fatal error: Cosa/OutputPin.hh: No such file or directory
compilation terminated.
Error compiling.

Any idea what I might be doing wrong?

Please select one of Cosa prefixed boards in the Board Menu. You are using standard "Arduino Uno". Try "Cosa Arduino Uno". Cheers!

Thank you! Geek weekend fun secured!