Add mutex_m dependency and update fast-stemmer version

- Add mutex_m gem to Gemfile and gemspec
- Update fast-stemmer dependency version in gemspec
- Remove explicit require of mutex_m in test_helper.rb

Gemfile

@@ -3,3 +3,4 @@ gemspec
 
 gem 'fast-stemmer'
 gem 'matrix'
+gem 'mutex_m'

Gemfile.lock

@@ -11,6 +11,7 @@ GEM
     fast-stemmer (1.0.2)
     matrix (0.4.2)
     minitest (5.18.1)
+    mutex_m (0.2.0)
     psych (5.1.2)
       stringio
     rake (13.0.6)
@@ -28,6 +29,7 @@ DEPENDENCIES
   fast-stemmer
   matrix
   minitest
+  mutex_m
   rdoc
 
 BUNDLED WITH

classifier.gemspec

@@ -9,7 +9,8 @@ Gem::Specification.new do |s|
   s.files = Dir['{lib}/**/*.rb', 'bin/*', 'LICENSE', '*.md', 'test/*']
   s.license = 'LGPL'
 
-  s.add_dependency 'fast-stemmer', '~> 1.0.0'
+  s.add_dependency 'fast-stemmer', '~> 1.0'
+  s.add_dependency 'mutex_m', '~> 0.2'
   s.add_dependency 'rake'
   s.add_development_dependency 'minitest'
   s.add_development_dependency 'rdoc'

test/test_helper.rb

@@ -1,6 +1,5 @@
 $:.unshift(File.dirname(__FILE__) + '/../lib')
 
-require 'mutex_m'
 require 'minitest'
 require 'minitest/autorun'
 require 'classifier'