Merge pull request #87 from jamon/master

add support for symlinking (junctions) on win32
Add ln support, including both -s and -f options.
Merge pull request #88 from Schoonology/ln

Add ln support, including both -s and -f options.
Add a regression test for ln treating abspaths badly.
Fix ln using bad paths when given abspaths.

path.join will produce a bad path if given an abspath like `/home/foo`.
path.resolve is what we really want.
Merge pull request #89 from Schoonology/ln-abspath-fix

Fix ln using bad paths when given abspaths.