fix to use syntax_trees_dir option
Merge pull request #50 from naoGreenTea/fix-output-dir-option

Fix output dir option
fixed README
fixed argument name
fixed message and used python 3.X style print
Extracted method: "check_and_make_working_dir"
Merge pull request #53 from niyaton/quick-fix-working-dir

Quick fix working dir
Storing syntax trees directory is now optional.
removed wasted statements
fixed README
Merge pull request #54 from niyaton/use-tempdir-for-syntax-trees-dir

Use tempdir for syntax trees dir