2.4.0

• only supports node's version >= 4.
• Refactor folder structure:
  • now ~/.lc/ would be the only folder used by leetcode-cli.
  • move lcconfig file to ~/.lc/.
  • move cache files to ~/.lc/cache/.
• config
  • fix string value parsing error.
• list
  • show tag/lang badges in -x output.
• show
  • add -q -t options to filter random questions.
• stat
  • enhance output of -g option.
  • enhance output on windows.
  • add -c option to display calendar stat of how many AC-ed questions per day.
  • add --no-lock option to filter out locked questions.
  • add -q -t options to filter questions stat.