Here lies the instrument for packing query bigrams into its current format. For
it to work you need to compile ../triecompiler as well and to run
compile_bigrams.sh. It tells you how to run it when run without arguments.
The input format is:

bigram_separated_by_underscore <TAB> WINDOW_QUERY_FREQ <TAB> QUERY_FREQ <TAB> TEXT_FREQ
