changed type to number for easier crossfilter operations
changed type to number for easier crossfilter operations

nlesc-sherlock/punchcardjs,nlesc-sherlock/spiraljs,nlesc-sherlock/punchcardjs-demo,nlesc-sherlock/punchcardjs-demo,nlesc-sherlock/spiraljs,nlesc-sherlock/punchcardjs,nlesc-sherlock/punchcardjs-demo,nlesc-sherlock/punchcardjs