document arguments

Author: dominictarr

README.md

@@ -33,6 +33,26 @@ pull(
 )
 ```
 
+## split(matcher, mapper, reverse, skipLast)
+
+### matcher - string or regexp.
+
+unit to split by, defaults to `\n`
+
+### mapper - function
+
+function to apply to each line matched.
+
+### reverse - boolean
+
+if true, emit lines in reverse. use this if the input is a file
+you are reading backwards.
+
+### skipLast - boolean
+
+use this to skip the last value if it is and empty string `''`
+if this is not set then the behavior is the same as `String#split`
+
 ## License
 
 MIT