Add webpack 4 support

• Add webpack 4 support (#14 @jimexist )

v0.2.2

• Fixed bug when publicPath starts with protocol (#10)

v0.2.1

• Fixed win path bug (cantonjs/wxapp-boilerplate#21)

v0.2.0

• Added enforceRelativePath option

v0.1.2

• Fixed minimize bug (#7 #8 #9)

v0.1.1

• Fixed <inline><block/></inline> bug when minimize: true (#6 by @jinker)

Add `transformContent()` and `transformUrl()` options

• Add transformContent() option
• Add transformUrl() option
• Deprecated format() option