Don't supress non-spring load errors in binstub

Without this change, the spring binstub supresses unrelated load errors,
eg. due to errors in initializers or loaded gems. This change causes the
binstub to only ignore a missing spring loader or gem.

Author: felixbuenemann

lib/spring/client/binstub.rb

@@ -13,8 +13,9 @@ class Binstub < Command
       # should cause the "unsprung" version of the command to run.
       LOADER = <<CODE
 begin
-  load File.expand_path('../spring', __FILE__)
-rescue LoadError
+  load spring_loader = File.expand_path('../spring', __FILE__)
+rescue LoadError => e
+  raise unless e.message.end_with? spring_loader, 'spring/binstub'
 end
 CODE