Improved Build.PL: used configure_requires and test_requires, stated
module versions for dependencies. Removed MANIFEST, to be generated at
distribution time.
Added manifest creation and dist build.

Updated MANIFEST.SKIP to avoid log files.
Restored MANIFEST because Build.PL issues warnings without it. It also
prevents test cruft ending up in the dist.
Added deployment key. Stopped MANIFEST rebuilding.
Merge pull request #5 from keithj/devel

Build improvements and distribution deployment