hardlink: Add formula for 0.2.0 & 0.3.0_rc1

Add formula for the hardlink project from http://jak-linux.org/projects/hardlink/.

Hardlink replaces multiple copies of a file with hardlinks. This formula includes both the stable and experimental versions.

References: 

A previous pull request was opened for the Python version but was closed in favor of a formula for the C version. https://github.com/mxcl/homebrew/pull/12068

There is also a pull request that was meant to let OS X users create actual hardlinks. https://github.com/mxcl/homebrew/pull/17134.