Fixed #332 Allow users to reset their password (#335)

* <Added password reset system>

* <Added rspec tests>

* <Fixed code style>

* <Added rescue for invalid smtp configuration>

app/mailers/user_mailer.rb

@@ -24,4 +24,10 @@ class UserMailer < ApplicationMailer
     @url = url
     mail(to: @user.email, subject: t('landing.welcome'))
   end
+
+  def password_reset(user, url)
+    @user = user
+    @url = url
+    mail to: user.email, subject: t('reset_password.subtitle')
+  end
 end