Don't auto-follow redirects when using curl

This has caught me out a few times when writing install scripts in
shared projects. Works for me but then fails for anyone who doesn't have
the same global curl configuration. Easier to stick to the defaults in
this case.

Fix #45
Don't use 'silent' by default for curl

It's nice to have some visual feedback that something is actually
happening.

Fix #43
vim: fix filetype for json files

Close #40