## Caseless -- wrap an object to set and get property with caseless semantics but also preserve caseing.
  
  This library is incredibly useful when working with HTTP headers. It allows you to get/set/check for headers in a caseless manner while also preserving the caseing of headers the first time they are set.
  
  ## Usage
  
  ```javascript
  var headers = {}
    , c = caseless(headers)
    ;
  c.set('a-Header', 'asdf')
  c.get('a-header') === 'asdf'
  ```
  
  ## has(key)
  
  Has takes a name and if it finds a matching header will return that header name with the preserved caseing it was set with.
  
  ```javascript
  c.has('a-header') === 'a-Header'
  ```
  
  ## set(key, value[, clobber=true])
  
  Set is fairly straight forward except that if the header exists and clobber is disabled it will add `','+value` to the existing header.
  
  ```javascript
  c.set('a-Header', 'fdas')
  c.set('a-HEADER', 'more', false)
  c.get('a-header') === 'fdsa,more'
  ```
  
  ## swap(key)
  
  Swaps the casing of a header with the new one that is passed in.
  
  ```javascript
  var headers = {}
    , c = caseless(headers)
    ;
  c.set('a-Header', 'fdas')
  c.swap('a-HEADER')
  c.has('a-header') === 'a-HEADER'
  headers === {'a-HEADER': 'fdas'}
  ```