duplicate the VERSION object so it can be stripped

should fix:
````
/Users/turadg/.rbenv/versions/1.9.3-p327-perf/lib/ruby/1.9.1/rubygems/ve
rsion.rb:191:in `strip!': can't modify frozen String (RuntimeError)
	from
/Users/turadg/.rbenv/versions/1.9.3-p327-perf/lib/ruby/1.9.1/rubygems/ve
rsion.rb:191:in `initialize'
	from
/Users/turadg/.rbenv/versions/1.9.3-p327-perf/lib/ruby/1.9.1/rubygems/ve
rsion.rb:178:in `new'
	from
/Users/turadg/.rbenv/versions/1.9.3-p327-perf/lib/ruby/1.9.1/rubygems/ve
rsion.rb:178:in `create'
	from
/Users/turadg/.rbenv/versions/1.9.3-p327-perf/lib/ruby/1.9.1/rubygems/sp
ecification.rb:2129:in `version='
	from
/Users/turadg/Code/Ruby/geknowm-rails/vendor/bundle/ruby/1.9.1/bundler/g
ems/schiphol-dce8ec894aaf/schiphol.gemspec:7:in `block in <main>'
````