Error: Could not symlink include/node/common.gypi
/usr/local/include/node is not writable.

Solution:

1. Simply run these four commands:
    ~# sudo chown -R `whoami`:admin /usr/local/include/node
    ~# sudo chown -R `whoami`:admin /usr/local/bin
    ~# sudo chown -R `whoami`:admin /usr/local/share
    ~# sudo chown -R `whoami`:admin /usr/local/lib/dtrace 
2. Finally, run the overwrite command:
    ~# brew link --overwrite node