Move logger instance to class var in FloatyLogger

This moves the instance of the logger class to a class variable in the
`FloatyLogger` class and provides three class methods to log with in the
rest of the project `FloatyLogger.info`, `FloatyLogger.warn`, and
`FloatyLogger.error`.

lib/vmfloaty/logger.rb

@@ -1,6 +1,22 @@
 require 'logger'
 
 class FloatyLogger < ::Logger
+  def self.logger
+    @@logger ||= FloatyLogger.new
+  end
+
+  def self.info(msg)
+    FloatyLogger.logger.info msg
+  end
+
+  def self.warn(msg)
+    FloatyLogger.logger.warn msg
+  end
+
+  def self.error(msg)
+    FloatyLogger.logger.error msg
+  end
+
   def initialize
     super(STDERR)
     self.level = ::Logger::INFO
@@ -8,4 +24,4 @@ class FloatyLogger < ::Logger
         "#{msg}\n"
     end
   end
-end
+end