function tap(value, interceptor) {
        interceptor(value);
        return value;
      }
This method invokes `interceptor` and returns `value`. The interceptor
is invoked with one argument; (value). The purpose of this method is to
"tap into" a method chain sequence in order to modify intermediate results.

@static
@memberOf _
@since 0.1.0
@category Seq
@param {*} value The value to provide to `interceptor`.
@param {Function} interceptor The function to invoke.
@returns {*} Returns `value`.
@example

_([1, 2, 3])
 .tap(function(array) {
   // Mutate input array.
   array.pop();
 })
 .reverse()
 .value();
// => [2, 1]