Fix typos (#236)

Author: sampatbadhe

doc/csv/options/generating/write_headers.rdoc

@@ -19,7 +19,7 @@ Without +write_headers+:
 
 With +write_headers+":
   CSV.open(file_path,'w',
-      :write_headers=> true,
+      :write_headers => true,
       :headers => ['Name','Value']
     ) do |csv|
       csv << ['foo', '0']

doc/csv/recipes/generating.rdoc

@@ -148,7 +148,7 @@ This example defines and uses a custom write converter to strip whitespace from
 
 ==== Recipe: Specify Multiple Write Converters
 
-Use option <tt>:write_converters</tt> and multiple custom coverters
+Use option <tt>:write_converters</tt> and multiple custom converters
 to convert field values when generating \CSV.
 
 This example defines and uses two custom write converters to strip and upcase generated fields:

doc/csv/recipes/parsing.rdoc

@@ -83,7 +83,7 @@ Use instance method CSV#each with option +headers+ to read a source \String one
   CSV.new(string, headers: true).each do |row|
     p row
   end
-Ouput:
+Output:
   #<CSV::Row "Name":"foo" "Value":"0">
   #<CSV::Row "Name":"bar" "Value":"1">
   #<CSV::Row "Name":"baz" "Value":"2">