Fix  typo in js method

For Pillow: CVE-2020-5313, CVE-2019-19911
For Django: CVE-2020-7471, CVE-2019-19844

Create a 404 page

Feature: Add naive plugin support for pinry

Refine some parameter names and fix doc in comments.

Convert Dockerfile to Multi-Stage & Update .gitignore

Decrease Dockefile image from 1.46GB to 325MB. Speed up the build by leveraging Docker Multi-Stage technique and using python:3.7-slim-stretch as final image.

This change ignores the docker generated data.

Use jsDelivr for MDI for better global speed

This is extremely useful for mainland Chinese users.

Also fix default value for privacy option of board and pin.

Ref: https://stackoverflow.com/questions/12009423/what-does-status-canceled-for-a-resource-mean-in-chrome-developer-tools

Update spelling of "pinned."

close #50 #115 search boards and pins by tag

close  #52 private pin and board