add TempfilePath class for finalizing Tempfile instance
remove @@tempfiles, Tempfile.delete_all, Tempfile.tempfiles
remove Tempfile#_set_path
fix Tempfile#size
refactor Tempfile#close!
add test, remove tempfile when run GC
remove Tempfile#open
add testcase, Tempfile#close(true)
Merge pull request #1 from iij/feature_remove_tempfile_finalizing_instance

Feature remove tempfile finalizing instance