Update https-proxy-agent to v3.0.0 (#47)

Fixes a MitM vulnerability in the module.

See: TooTallNate/proxy-agents#77

Author: adrukh

package.json

@@ -32,7 +32,7 @@
     "agent-base": "^4.2.0",
     "debug": "^3.1.0",
     "http-proxy-agent": "^2.1.0",
-    "https-proxy-agent": "^2.2.1",
+    "https-proxy-agent": "^3.0.0",
     "lru-cache": "^4.1.2",
     "pac-proxy-agent": "^3.0.0",
     "proxy-from-env": "^1.0.0",