marmalade-service.el: Set error status.

* marmalade-service.el (marmalade/package-blurb): Return a 500 status
  instead of 200 if an internal error happened.
marmalade-service.el: Use `expand-file-name'.

* marmalade-service.el (marmalade/upload-page)
  (marmalade/login-sender, marmalade/webserver)
  (marmalade/special-docs): Use `expand-file-name' instead of `concat'.
  (marmalade/save-package): Replace `insert-string' (obsolete since
  "22.1") with `insert'.
Merge pull request #8 from ruediger/minorfixes

Minor Fixes