Parser global leak

Exports.parse contained a variable that didn't have a var statement. It gets picked up by Mocha as a global leak. It is not a global leak per se but it is a leak within the nmea.js file and might lead to weird behaviour in the future.
Merge pull request #8 from jksdua/master

Parser global leak
Merge branch 'master' of https://github.com/jamesp/node-nmea