changend deprecated File.exists method calls to File.exist

see also issue Gazler#337 and https://stackoverflow.com/questions/14351272/undefined-method-exists-for-fileclass-nomethoderror/75353113#75353113

lib/githug/cli.rb

@@ -97,7 +97,7 @@ def make_directory!
       end
 
       def check_githug_directory!
-        if File.exists?("./git_hug")
+        if File.exist?("./git_hug")
           UI.puts "Please change into the git_hug directory"
           exit
         end

lib/githug/level.rb

@@ -35,7 +35,7 @@ def setup(path)
         level_path = path.chomp(File.extname(path))
         level = self.new
 
-        return false unless File.exists?(path)
+        return false unless File.exist?(path)
 
         level.instance_eval(File.read(path))
         level.level_name = File.basename(path, File.extname(path))

lib/githug/profile.rb

@@ -13,7 +13,7 @@ def load
       private
 
       def settings
-        return defaults unless File.exists?(PROFILE_FILE)
+        return defaults unless File.exist?(PROFILE_FILE)
         defaults.merge(YAML::load(File.open(PROFILE_FILE)))
       end
 

lib/githug/repository.rb

@@ -20,7 +20,7 @@ def reset
     end
 
     def create_gitignore
-      Dir.chdir("git_hug") if File.exists?("./git_hug")
+      Dir.chdir("git_hug") if File.exist?("./git_hug")
       File.open(".gitignore", "w") do |file|
         file.puts(".profile.yml")
         file.puts(".gitignore")