* Changed LoadError to Fog::Error::LoadError when missing configuration

* When running from command line, rescue the exception, and print the help message

When running fog for the first time with no setup, the missing_exception message
was surrounded above and below with a stack trace, which is not particularly
user-friendly. Since we've rescuing the LoadError only in bin/fog, we know
we don't have to worry about higher level libraries not getting the exception,
since it wouldn't propagate between processes.

Changing LoadError to Fog::Error::LoadError lets us know that this was
an issue on fog's part, rather than some other library we might be
using. Since we inherit from the LoadError class, any higher-level
libraries that were using a rescue based on LoadError will still work.

bin/fog

@@ -5,7 +5,11 @@ require 'yaml'
 Fog.credential = ARGV.first ? ARGV.first.to_sym : nil
 Fog.mock! if ENV['FOG_MOCK']
 if Fog.credentials.empty?
-  Fog::Errors.missing_credentials
+  begin
+    Fog::Errors.missing_credentials
+  rescue Fog::Errors::LoadError => error
+    abort error.message
+  end
 end
 
 require 'fog/bin'

lib/fog/core/errors.rb

@@ -16,6 +16,8 @@ module Fog
 
     class NotFound < Fog::Errors::Error; end
 
+    class LoadError < LoadError; end
+
     # @return [String] The error message that will be raised, if credentials cannot be found
     def self.missing_credentials
       missing_credentials_message = <<-YML
@@ -68,7 +70,7 @@ An alternate file may be used by placing its path in the FOG_RC environment vari
 #######################################################
 
     YML
-    raise(LoadError.new(missing_credentials_message))
+    raise(Fog::Errors::LoadError.new(missing_credentials_message))
   end
 
   end