A log tool in console with 4 levels.
npm install @zppack/logA log tool in console with 4 levels.

- [x] colors log using chalk
- [x] 4 log levels
- [x] debug mode support
``sh`
npm install --save @zppack/log
`js
import log from '@zppack/log';
log.i('this is a info-level log');
log.info('this is also a info-level log');
`
#### log.info
Info-level log function. Shorted as log.i.
#### log.warn
Warn-level log function. Shorted as log.w.
#### log.error
Error-level log function. Shorted as log.e.
#### log.debug
Debug log function. Shorted as log.d.
Attention: Only works when there is an env variable process.env.DEBUG or process.env.ZP_DEBUG` set to true.
See the change log.