Bump required tap version to 0.4.1

When using node 0.10, test initiation will fail due to differences in
the array.map function.  This discrepancy is corrected in tap v0.4.1.
See: https://github.com/isaacs/node-tap/issues/70
Merge pull request #150 from pfmooney/tests-tap-version

Fixes #139 - Bump required tap version to 0.4.1