#389 fix grammar

Author: Mifrill

README.md

@@ -156,17 +156,16 @@ sheet.to_xml
 sheet.to_yaml
 ```
 
-You can specified file as default argument to `#to_csv`: 
+Specify the file as default argument for `#to_csv`:
 
 ```ruby
-# puts csv format content into a specified file
 sheet.to_csv(File.new("/dev/null"))
 ```
 
-also you can specify the custom separator for the content:
+specify the custom separator:
 
 ```ruby
-sheet.to_csv(separator: ":") # "," is used by default
+sheet.to_csv(separator: ":") # "," using by default
 ```
 
 ### Excel (xlsx and xlsm) Support