feat: Rename plugins option to parser-plugins. (#1031)

The original option name created confusion about what was expected.
This helps identify that babel parser plugins are expected, not babel
transform plugins.

BREAKING CHANGE: The `plugins` option has been renamed to
`parser-plugins`.

Fixes #986

index.js

@@ -136,7 +136,7 @@ NYC.prototype._createInstrumenter = function () {
     compact: this.config.compact,
     preserveComments: this.config.preserveComments,
     esModules: this.config.esModules,
-    plugins: this.config.plugins
+    plugins: this.config.parserPlugins
   })
 }
 

lib/hash.js

@@ -7,7 +7,7 @@ function getInvalidatingOptions (config) {
     'ignoreClassMethods',
     'instrument',
     'instrumenter',
-    'plugins',
+    'parserPlugins',
     'preserveComments',
     'produceSourceMap',
     'sourceMap'

lib/instrumenters/istanbul.js

@@ -5,7 +5,7 @@ const convertSourceMap = require('convert-source-map')
 const mergeSourceMap = require('merge-source-map')
 
 function InstrumenterIstanbul (cwd, options) {
-  const plugins = options.plugins
+  const plugins = options.parserPlugins
   const configPlugins = plugins ? { plugins } : {}
 
   const instrumenter = createInstrumenter(Object.assign({