gemspec: fixed license name, semantic versioned dependency for ffi

discid.gemspec

@@ -11,7 +11,7 @@ Gem::Specification.new do |spec|
   spec.description   = %q{ruby-discid provides Ruby bindings for the MusicBrainz DiscID library libdiscid. It allows calculating DiscIDs (MusicBrainz and freedb) for Audio CDs. Additionally the library can extract the MCN/UPC/EAN and the ISRCs from disc.}
   spec.summary       = %q{Ruby bindings for libdiscid}
   spec.homepage      = "https://github.com/phw/ruby-discid"
-  spec.license       = "LGPL-3"
+  spec.license       = "LGPL-3.0"
   spec.post_install_message = %q{Please make sure you have libdiscid (http://musicbrainz.org/doc/libdiscid) installed.}
 
   spec.requirements              = "libdiscid >= 0.1.0"
@@ -24,7 +24,7 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "ffi", ">= 1.6.0"
+  spec.add_dependency "ffi", "~> 1.6"
 
   spec.add_development_dependency "rake"
   spec.add_development_dependency "bundler", ">= 1.3"