Update default devise wording to include reference to Mastodon

Fix #68

app/views/auth/mailer/confirmation_instructions.html.erb

@@ -1,5 +1,5 @@
 <p>Welcome <%= @resource.email %>!</p>
 
-<p>You can confirm your account email through the link below:</p>
+<p>You can confirm your Mastodon account email through the link below:</p>
 
 <p><%= link_to 'Confirm my account', confirmation_url(@resource, confirmation_token: @token) %></p>

app/views/auth/mailer/password_change.html.erb

@@ -1,3 +1,3 @@
 <p>Hello <%= @resource.email %>!</p>
 
-<p>We're contacting you to notify you that your password has been changed.</p>
+<p>We're contacting you to notify you that your password on Mastodon has been changed.</p>

app/views/auth/mailer/reset_password_instructions.html.erb

@@ -1,6 +1,6 @@
 <p>Hello <%= @resource.email %>!</p>
 
-<p>Someone has requested a link to change your password. You can do this through the link below.</p>
+<p>Someone has requested a link to change your password on Mastodon. You can do this through the link below.</p>
 
 <p><%= link_to 'Change my password', edit_password_url(@resource, reset_password_token: @token) %></p>
 

config/locales/devise.en.yml

@@ -18,13 +18,13 @@ en:
       unconfirmed: "You have to confirm your email address before continuing."
     mailer:
       confirmation_instructions:
-        subject: "Confirmation instructions"
+        subject: "Mastodon: Confirmation instructions"
       reset_password_instructions:
-        subject: "Reset password instructions"
+        subject: "Mastodon: Reset password instructions"
       unlock_instructions:
-        subject: "Unlock instructions"
+        subject: "Mastodon: Unlock instructions"
       password_change:
-        subject: "Password Changed"
+        subject: "Mastodon: Password Changed"
     omniauth_callbacks:
       failure: "Could not authenticate you from %{kind} because \"%{reason}\"."
       success: "Successfully authenticated from %{kind} account."