Require snakemake < 5.6 so it doesn't break things

Snakemake has gained a very unstable dependency called "pulp" that
doesn't work on Python 3.8. We've found in other repositories that
it's better to restrict Snakemake to versions below 5.6.

Prevent XSS in JSON-LD

Data update for ConceptNet 5.8

Minor changes to Web interface

This commit expands the file that excludes certain patterns of
assertions from ConceptNet, now called the "blocklist".

This commit involves adding a number of racial and sexual slurs to the
blocklist, and they appear in plain text in the file, so beware.

This example was originally added as a memorial to Marvin Minsky. The
context for it has passed.

Also, ConceptNet isn't designed for named entities, and this example
gives the misleading impression that it is. We'll replace it with
an example that shows that ConceptNet understands emoji.

improvements to documentation and JSON formatting

ignore too-short term names from word2vec input

update the vector space export process, fixing Korean