linkify URLs in invite email

mail-src/invite

@@ -10,12 +10,12 @@ It's great for meeting new people who share your interests.
 
 You can see %%arg.inviter%%'s profile page on %%site.name%% here:
 
-    %%arg.inviterurl%%
+   [%%arg.inviterurl%%](%%arg.inviterurl%%)
 
 If you'd like to try the service, click on the link below to accept
 the invitation.
 
-    %%arg.confirmurl%%
+    [%%arg.confirmurl%%](%%arg.confirmurl%%)
 
 If not, you can ignore this message. Thanks for your patience and your time.
 

mail-src/invitepersonal

@@ -14,12 +14,12 @@ They said:
 
 You can see %%arg.inviter%%'s profile page on %%site.name%% here:
 
-    %%arg.inviterurl%%
+   [%%arg.inviterurl%%](%%arg.inviterurl%%)
 
 If you'd like to try the service, click on the link below to accept
 the invitation.
 
-    %%arg.confirmurl%%
+    [%%arg.confirmurl%%](%%arg.confirmurl%%)
 
 If not, you can ignore this message. Thanks for your patience and your time.