Rename Apt Codename to "raspotify" from "jessie" (which was confusing…

… + old)

However, we'll keep jessie for backward compatibility as to not break older
installations

Fixed cross-compiling of alsa-sys (closes dtcooper#192)

Use working ftp mirror

Troubleshooting: Added note about USB sound cards

less strict OS checking

Add note about testing on B+

Re-address dtcooper#91 and remove all references to 0755

Temporarily use @dawidd6 for a fix

Don't strip so we get tracebacks

Allow for alternate backends, such as pipe. Fixes dtcooper#83