Fix NodeJS 8 (engines/node) in package.json
Fix NodeJS 8 (engines/node) in package.json

Fix requiring NodeJS 8 or later, as per intent of https://github.com/Microsoft/tfs-cli/commit/11745aa9a0d4790f23892a59141b40a02fa8f209.

Fixes https://github.com/Microsoft/tfs-cli/issues/288
Microsoft/tfs-cli,grawcho/tfs-cli,grawcho/tfs-cli,Microsoft/tfs-cli,grawcho/tfs-cli