support http and https protocols for remote tilejson. refs #61
test for http and https source protocols
ignore node_modules directory
support postgis port
More thorough remote check
De-dupe logic
Merge pull request #71 from Caged/postgis-port

Add option for Postgres port
Merge pull request #76 from mojodna/source-tilejson

HTTP/HTTPS vector tile sources
Update for v4.
Add format key to source metadata.
Source v3 => v4.
Don't cache when exporting.