Adding Exposed headers for CORS

By default, when doing CORS ajax request, following headers will be available:

 - Cache-Control
 - Content-Language
 - Content-Type
 - Expires
 - Last-Modified
 - Pragma

[source](http://www.w3.org/TR/cors/#simple-response-header)

[more info - point 4](http://www.w3.org/TR/cors/#resource-requests)

if we need to read anything else from headers (even-thou they are returned) we need to provide `Access-Control-Expose-Header`, otherwise browsers will not allow to get these headers from xhr response.

Exact case: [SO question](http://stackoverflow.com/questions/17038436/reading-response-headers-when-using-http-of-angularjs)

Im not sure if there are other headers that will need to be exposed, but `Location` is required for getting information about created projection
Merge pull request #94 from Gutek/patch-2

Adding Exposed headers for CORS