Housekeeping: restructured format to be more manageable
Housekeeping: restructured files meant scoping private/public functions became difficult.  Reverted to single file
Refactoring: Moved parameter validations into separate non-export functions.  Introduced private constants for validation values
Refactored query string encoding and simpler base method for all requests
Load System.Web assembly through manifest
Function to URL encode a hashtable  and better parsing of result item
Refactored url formatting and header construction
Stubbed Add method.  Removed '?' from Format-UrlEncoded so it can be used for the body.  Renamed $fields to $responseFields
Removed validation from Invoke-SitecoreRequest - acts as raw access to the api.

Completed Add method
Ensure content type is handled correctly.

Functions for getting/setting a Sitecore item.
Fixed Test-Guid check.

Created Remove-SitecoreItem function and normalised DELETE 200 response with normal 200 response for consistency
Added paging validation.

Housekeeping: Documentation of methods
Updated README with latest install instructions and help
Merge branch 'develop'