Fix for not following enough redirect links (#62)

[dougli1sqrd]

Fix for https://github.com/jeff-hughes/shellcaster/issues/62

• when downloading a podcast, the http agent will now follow up to 10 redirects
• fixed a few instances of error: non-binding let on a synchronization lock

[Elcoid]

I confirm that this solves #62 (and its duplicate #63) on my side.

[luvchurchill]

Can confirm it solves it for me too. Thanks! was really bugging me

[Elcoid]

Just for information, I pulled this PR in my fork of Shellcaster: https://github.com/Elcoid/shellcaster-classic