Homebrew installation question for PostgreSQL 9.4.1 (OS X 10.10.2)

Hi

I tried to install PostgreSQL 9.4.1 using homebrew on my Mac (running OS X 10.10.2)
but I don’t it was complete. The caveats listing included the following error

Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
Could not symlink include/ecpg_config.h
/usr/local/include is not writable.

You can try again using:
brew link postgresql
==> /usr/local/Cellar/postgresql/9.4.1/bin/initdb /usr/local/var/postgres
==> Summary
🍺 /usr/local/Cellar/postgresql/9.4.1: 2996 files, 40M

I tried doing

sudo brew link postgresql

but I received the following error

Error: Cowardly refusing to `sudo brew link`
You can use brew with sudo, but only if the brew executable is owned by root.
However, this is both not recommended and completely unsupported so do so at
your own risk.

Any help appreciated.

SM