decompose conditional by using De Morgan's laws
we can use newer hash syntax because fluentd requires ruby version >= 1.9.3
we can use lambda literal because fluentd requires ruby version >= 1.9.3
superclass's shutdown is called even without this code
don't repeat yourself
redundant code
copy and paste
Merge pull request #32 from tanimichi/refactoring_out_bigquery

Refactoring of out_bigquery.rb