Changes:
README.md
Informal documentation of how to initiate PCFG experiments
count_cfg_freq.py and eval_parser (slightly modified) by Alex Rush
filtering.py to filter out sentences by length
pcfg_parser.py is to parse a given set of sentences in parallel
retag.py is to set postage of words in a JSON parse tree
split.py is to split a given corpus as training(.train) and test sets (.dev .key)
tree2json.py is to convert treebank format to JSON format
tree2sentence.py is to convert a JSON tree to a flattened sentence with/without postage
upos_map.py is used by retag.py to set word postags given in a file