Update gemspec, Readmill => readmill

Author: auroranockert

readmill.gemspec

@@ -5,7 +5,7 @@ $:.unshift lib unless $:.include?(lib)
 require 'readmill/version'
 
 Gem::Specification.new do |s|
-  s.name        = "Readmill"
+  s.name        = "readmill"
   s.version     = Readmill::VERSION
   s.platform    = Gem::Platform::RUBY
 
@@ -21,4 +21,4 @@ Gem::Specification.new do |s|
   s.add_dependency('rest-client')
 
   s.require_path = 'lib'
-end
+end