Creates a unary function wrapper which extracts a specific argument by index and applies the argument to the original unary function.
npm install unary  
``shell`
npm install unary --save
###### npm stats
  
###### require
`js`
var unary = require('unary')
###### full application
`js
var odds = unary(odd, 1)
var fruit = [ 'apple', 'pear', 'pineapple', 'strawberry', 'orange', 'grapefruit' ]
fruit.filter(odds)
//=> [ 'apple', 'pineapple', 'orange' ]
`
###### functor (+ partial application)
`js
var evens = unary(even)
var fruit = [ 'apple', 'pear', 'pineapple', 'strawberry', 'orange', 'grapefruit' ]
fruit.filter(evens(1))
//=> [ 'pear', 'strawberry', 'grapefruit' ]
`
###### arguments
- fun: (Function) Unary function to wrap.idx: (Number)
- Index of argument to extract.
###### returns
- (Function)` Wrapped unary function.
