Fix sprockets.gemspec to include MIT-LICENSE
Fix sprockets.gemspec to include MIT-LICENSE

The original License should be included in all packages of shoulda-matchers. The current gemspec does so by including "MIT-LICENSE"-File which doesn't exist. This commit fixes that referencing the "LICENSE"-File.
thoughtbot/shoulda-matchers,biow0lf/shoulda-matchers,biow0lf/shoulda-matchers,biow0lf/shoulda-matchers,thoughtbot/shoulda-matchers,thoughtbot/shoulda-matchers,biow0lf/shoulda-matchers,thoughtbot/shoulda-matchers