feat(plugins): normalize plugins and have unified function signature

src/lib/plugins.js

@@ -0,0 +1,17 @@
+let exports = module.exports = function (source) {
+  return {
+    analyze: exports.normalize(source.analyze, '@semantic-release/commit-analyzer'),
+    generateNotes: exports.normalize(source.analyze, '@semantic-release/release-notes-generator'),
+    verify: exports.normalize(source.verify, './plugin-noop')
+  }
+}
+
+exports.normalize = function (plugin, fallback) {
+  if (typeof plugin === 'string') return require(plugin).bind(null, {})
+
+  if (plugin && (typeof plugin.path === 'string')) {
+    return require(plugin.path).bind(null, plugin)
+  }
+
+  return require(fallback).bind(null, plugin)
+}