upgrade diff to v3.5

[rob-balfre]

@axross Github is complaining that tap-diff has a security vulnerability. Can you upgrade the diff dependency to version 3.5.0 or later please.

[mindplay-dk]

@axross are you still maintaining this project? if not, I don't want to submit a PR.

[githubjosh]

this security patch is pretty urgent. should be a quick update, no?

diff  <3.5.0
Severity: high
Regular Expression Denial of Service (ReDoS) - https://github.com/advisories/GHSA-h6ch-v84p-w6p9
fix available via `npm audit fix --force`
Will install tap-diff@0.0.0, which is a breaking change
node_modules/tap-diff/node_modules/diff
  tap-diff  >=0.0.1
  Depends on vulnerable versions of diff
  node_modules/tap-diff