Add tests, fix empty cert bug, improve packaging

This is version 0.2.1.

- Add mostly complete unit testing using mock objects, and integrate
  testing with http://travis-ci.org.
- Fix handling of an edge case where get PeerCertificate() returns an
  empty certificate. Close #1.
- Improve package.json to be more complete and correct.

Squashed commit of the following:

commit 4139e2170c6d7d4ed6b8a847b9835c524a41febd
Author: Tony Gies <tgies@tgies.net>
Date:   Sat May 4 20:18:33 2013 -0500

    Handle the empty-cert-object case. Close #1.

    Fix the cert test to correctly handle the case that the object returned
    by req.getPeerCertificate() is an empty object. See
    https://github.com/tgies/client-cert-auth/issues/1 for more information.

commit 1f59990fc5a06bf2e33cca76fe8a6ca862b1255f
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 23:43:18 2013 -0500

    Fix typos in test/test-unit-clientCertificateAuth.js

    - Copyedit comment.
    - Remove spurious comma in mockUn*Req hashes.

commit 5cbd23e1562c5eb5501db7ee62d4cfe1854b687c
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 21:34:17 2013 -0500

    Enhanced/extra/corrected/more readable tests

    - Add a few tests for error conditions
    - Reword some existing tests
    - New mock requests to support new tests
    - More readable test code, hopefully

commit 756b8cfd827f81783b7662f36f6375a5618b4676
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 15:46:56 2013 -0500

    Add http://travis-ci.org status image

commit 5318934ebcacf25dcf174bb8245520cb818ae95a
Merge: fe6bcf9 7186f17
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 15:21:45 2013 -0500

    Merge branch 'feature-travis' into develop

commit 7186f1751ed0775629d8dd83adc4fbf8a140281a
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 15:20:55 2013 -0500

    Add .travis.yml for http://travis-ci.org

commit 5e580108b54ae60840f0c6e02bc557cf7b94eb1f
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 14:17:24 2013 -0500

    More correct and complete package.json

    package.json now includes devDependencies, supports testing, and
    contains additional useful metadata.

commit fe6bcf9cdd9c13bed6d8340642b20b933b410a0b
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 14:17:24 2013 -0500

    More correct and complete package.json

    package.json now includes devDependencies, supports testing, and
    contains additional useful metadata.

commit 1c3127092a2de3c2238c24191245ec8bc9288cbb
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 00:58:31 2013 -0500

    i am not Fond of swapfiles.

commit dc88decc5dec10602a9c991b982cb0f0b416519f
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 00:57:59 2013 -0500

    clarification

commit e54155532f2d4119334f6e5fb5d7a7a9902753a7
Author: Tony Gies <tgies@tgies.net>
Date:   Fri May 3 00:37:01 2013 -0500

    very basic and incomplete unit testing