added time interval filter

angular.module('cerebro').filter('timeInterval', function() {

  var UNITS = ['yr', 'mo', 'd', 'h', 'min'];

  var UNIT_MEASURE = {

    yr: 31536000000,

    mo: 2678400000,

    wk: 604800000,

    d: 86400000,

    h: 3600000,

    min: 60000

  };

  function stringify(seconds) {

    var result = 'less than a minute';

    for (var idx = 0; idx < UNITS.length; idx++) {

      var amount = Math.floor(seconds / UNIT_MEASURE[UNITS[idx]]);

      if (amount) {

        result = amount + UNITS[idx] + '.';

        break;

      }

    }

    return result;

  }

  return function(seconds) {

    return stringify(seconds);

  };

});