Raise shapefile file size limit, and add Reader.close() test

Author: karimbahgat

shapefile.py

@@ -1800,7 +1800,10 @@ def __shpRecord(self, s):
     def __shxRecord(self, offset, length):
          """Writes the shx records."""
          f = self.__getFileObj(self.shx)
-         f.write(pack(">i", offset // 2))
+         try:
+             f.write(pack(">i", offset // 2))
+         except error:
+             raise ShapefileException('The .shp file has reached its file size limit > 4294967294 bytes (4.29 GB). To fix this, break up your file into multiple smaller ones.')
          f.write(pack(">i", length))
 
     def record(self, *recordList, **recordDict):