fix #1

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# with '#' will be kept; you may remove them yourself if you want to.
# An empty message aborts the commit.
# On branch master
# Changes to be committed:
#   (use "git reset HEAD^1 <file>..." to unstage)
#
#	modified:   fluent-plugin-datacalculator.gemspec
#	modified:   lib/fluent/plugin/out_datacalculator.rb
#
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#	modified:   lib/fluent/plugin/out_datacalculator.rb
#
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#	data.log
#	ftp.xfer_log
#	hoge.conf
#	xfer.log
#	xfer.log.pos