Fix license

Author: quentinlesceller

blockcypher-ruby.gemspec

@@ -4,7 +4,7 @@ Gem::Specification.new do |s|
   s.name        = 'blockcypher-ruby'
   s.summary     = 'Blockcypher Ruby SDK'
   s.version     = '0.2.6'
-  s.licenses    = ['Apache 2.0']
+  s.licenses    = ['Apache-2.0']
   s.description = 'Ruby library to help you build your crypto application on BlockCypher'
   s.summary     = 'Ruby library to help you build your crypto application on BlockCypher'
   s.authors     = %w[CoinHako BlockCypher meXBT Gem]