code: function mergeEq(value, fieldMatchers) {
    // these all have less specificity than the $eq
    // TODO: check for user errors here
    delete fieldMatchers.$gt;
    delete fieldMatchers.$gte;
    delete fieldMatchers.$lt;
    delete fieldMatchers.$lte;
    delete fieldMatchers.$ne;
    fieldMatchers.$eq = value;
  }
docs: add $eq into the mix