[core] Splits Fog::VERSION into own file

Now available within "fog/core"

Just reverted a change where depending on Fog::VERSION for the
User-Agent made a dependency on requiring "lib/fog" which also requires
all providers and services.

That is highly undesirable from a modular perspective!

lib/fog.rb

@@ -1,11 +1,6 @@
 require File.join(File.dirname(__FILE__), 'fog', 'core')
 
 module Fog
-
-  unless const_defined?(:VERSION)
-    VERSION = '1.7.0'
-  end
-
 end
 
 # FIXME: these should go away (force usage of Fog::[Compute, CDN, DNS, Storage]  etc)

lib/fog/core.rb

@@ -15,6 +15,7 @@ require 'time'
 require 'timeout'
 
 # internal core dependencies
+require "fog/version"
 require 'fog/core/attributes'
 require 'fog/core/collection'
 require 'fog/core/connection'

lib/fog/version.rb

@@ -0,0 +1,5 @@
+module Fog
+  unless const_defined?(:VERSION)
+    VERSION = '1.7.0'
+  end
+end