Replace require with import

lib/index.js

@@ -1,12 +1,9 @@
 import path from 'path'
 import mkdirp from 'mkdirp'
-
-var spawn = require('child_process').spawn
+import { spawn } from 'child_process'
 
 var phantomscript = path.join(__dirname, 'phantomscript.js')
 
-module.exports = { process: processMermaid }
-
 function processMermaid (files, _options, _next) {
   var options = _options || {}
   var outputDir = options.outputDir || process.cwd()
@@ -41,3 +38,5 @@ function processMermaid (files, _options, _next) {
     phantom.stdout.pipe(process.stdout)
   })
 }
+
+export default { process: processMermaid }