Cleaned tab indents by 2 spaces.
Changed comment and let it alert when program starts.
Replaced ``import os`` by ``from os import ...``
Init
Added ``file2str`` function.
Fixed bug of pattern.
Added ``blank`` function.
Used ``file2list``
Fixed test files' relative path to absolute path and test running file2json.
Fixed bug that warning message should be stderr and not be written to json.
JSON file don`t need to contain root_dir