Small tweak to package.json fixes Windows error for 'npm test'

Windows doesn't like dot slash notation, so I swapped `./` for `node` in `package.json` to fix this. I'm happy to report that all of the unit tests pass in Windows!

    $ npm test

    > data2xml@0.8.0 test c:\Documents and Settings\apenneba\Desktop\node-data2xml
    > node node_modules/tap/bin/tap.js test/*.js

    ok test/basics.js ....................................... 8/8
    ok test/config-2.js ..................................... 5/5
    ok test/config.js ....................................... 3/3
    ok test/doc-xml.js ...................................... 2/2
    ok test/load.js ......................................... 2/2
    ok test/xml-generation.js ............................. 14/14
    total ................................................. 34/34

    ok