Dino catalog

Actually I tried to use just `method()` before using `lambda(&method())` and I got this message. I am not sure why this happen, because `Method` class contains `arity` method.
```
~/workspace/level_up_exercises/dino_catalog $  git diff -u
diff --git a/dino_catalog/dinosaur_parser.rb b/dino_catalog/dinosaur_parser.rb
index b5eaf5e..fcbec84 100644
--- a/dino_catalog/dinosaur_parser.rb
+++ b/dino_catalog/dinosaur_parser.rb
@@ -54,7 +54,8 @@ class DinosaurParser
   def header_converters
     [
       ->(h) { h.downcase },
-      lambda(&method(:dinosaur_header_converter)),
+      #lambda(&method(:dinosaur_header_converter)),
+      method(:dinosaur_header_converter),
       :symbol,
     ]
   end
~/workspace/level_up_exercises/dino_catalog $  ./main.rb -f african_dinosaur_export.csv
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:2166:in `block (2 levels) in convert_fields': undefined method `arity' for nil:NilClass (NoMethodError)
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:2165:in `each'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:2165:in `block in convert_fields'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:2164:in `map'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:2164:in `with_index'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:2164:in `convert_fields'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:2205:in `parse_headers'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1881:in `block in shift'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1773:in `loop'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1773:in `shift'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1715:in `each'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1729:in `to_a'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1729:in `read'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1323:in `block in read'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1266:in `open'
	from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/csv.rb:1323:in `read'
	from /Users/amahakumarage/workspace/level_up_exercises/dino_catalog/dinosaur_parser.rb:24:in `initialize'
	from ./main.rb:13:in `new'
	from ./main.rb:13:in `block in <main>'
	from ./main.rb:12:in `each'
	from ./main.rb:12:in `<main>'
```