Confirm to trust certificate when there is error

For #26

src/main/certificateStore.js

@@ -0,0 +1,62 @@
+'use strict';
+
+const fs = require('fs');
+const url = require('url');
+
+function comparableCertificate(certificate) {
+  return {
+    data: certificate.data.toString(),
+    issuerName: certificate.issuerName
+  };
+}
+
+function areEqual(certificate0, certificate1) {
+  if (certificate0.data !== certificate1.data) {
+    return false;
+  }
+  if (certificate0.issuerName !== certificate1.issuerName) {
+    return false;
+  }
+  return true;
+}
+
+function getHost(targetURL) {
+  return url.parse(targetURL).host;
+}
+
+var CertificateStore = function(storeFile) {
+  this.storeFile = storeFile
+  try {
+    this.data = JSON.parse(fs.readFileSync(storeFile, 'utf-8'));
+  }
+  catch (e) {
+    console.log(e);
+    this.data = {};
+  }
+};
+
+CertificateStore.prototype.save = function() {
+  fs.writeFileSync(this.storeFile, JSON.stringify(this.data, null, '  '));
+};
+
+CertificateStore.prototype.add = function(targetURL, certificate) {
+  this.data[getHost(targetURL)] = comparableCertificate(certificate);
+};
+
+CertificateStore.prototype.isExisting = function(targetURL) {
+  return this.data.hasOwnProperty(getHost(targetURL));
+};
+
+CertificateStore.prototype.isTrusted = function(targetURL, certificate) {
+  var host = getHost(targetURL);
+  if (!this.isExisting(targetURL)) {
+    return false;
+  }
+  return areEqual(this.data[host], comparableCertificate(certificate));
+};
+
+module.exports = {
+  load: function(storeFile) {
+    return new CertificateStore(storeFile);
+  }
+};