Clean up dependencies and remove lodash (#22)

Author: wilwade

lib/reader.js

@@ -1,6 +1,4 @@
 'use strict';
-const fs = require('fs');
-const thrift = require('thrift');
 const Int64 = require('node-int64');
 const parquet_thrift = require('../gen-nodejs/parquet_types')
 const parquet_shredder = require('./shred')
@@ -11,7 +9,6 @@ const parquet_compression = require('./compression')
 const parquet_types = require('./types');
 const BufferReader = require('./bufferReader');
 const bloomFilterReader = require('./bloomFilterIO/bloomFilterReader');
-const groupBy = require("lodash/groupBy");
 const fetch = require('cross-fetch');
 
 const {
@@ -235,7 +232,11 @@ class ParquetReader {
 
   async getBloomFiltersFor(columnNames) {
     const bloomFilterData = await getBloomFiltersFor(columnNames, this.envelopeReader);
-    return groupBy(bloomFilterData, 'columnName');
+    return bloomFilterData.reduce((acc, value) => {
+      if (acc[value.columnName]) acc[value.columnName].push(value)
+      else acc[value.columnName] = [value]
+      return acc;
+    }, {});
   }
 
   /**