wait-on issue doesn't play well with webpack-dev-server

[hegelstad]

💥 Regression Report

Last working version

Worked up to version: 4.0.0

Stopped working in version: 4.0.0

To Reproduce

Steps to reproduce the behavior:
Use webpack-dev-server and expect tests to start after compilation
The new wait-on package will not be able to parse the ok 200 status because it only listens for HEAD requests not GET requests... see https://github.com/bahmutov/start-server-and-test#note-for-webpack-dev-server-users

Expected behavior

It should work like before changing to wait-on

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## System:
 - OS: macOS Mojave 10.14.3
 - CPU: (4) x64 Intel(R) Core(TM) i5-7267U CPU @ 3.10GHz
 - Memory: 1.24 GB / 16.00 GB
 - Shell: 5.3 - /bin/zsh
## Binaries:
 - Node: 11.12.0 - /usr/local/bin/node
 - Yarn: 1.15.2 - ~/.yarn/bin/yarn
 - npm: 6.7.0 - /usr/local/bin/npm
 - Watchman: 4.9.0 - /usr/local/bin/watchman
## npmPackages:
 - jest-puppeteer: 4.1.1 => 4.1.1

[xiaoyuhen]

hi @hegelstad

I am very sorry that we upgraded wait-on and caused some issues on your project.

After my tests, this #235 PR will solve this issue.

We will release a new version as soon as possible.

see #233