Fix for improper path encoding

[andrueastman]

Fixes #553

Changes proposed in this pull request

• Encode the path segment of the URI to ensure special characters are sorted out in accordance with the one drive expectations
• Adds tests to verify the URL

Therefore making a call in the code as follows should now NOT fail with an error.

var session = await client.Drives[DriveId].Root.ItemWithPath("Test#1.txt").CreateUploadSession().Request().PostAsync();

Other links

• https://docs.microsoft.com/en-us/onedrive/developer/rest-api/concepts/addressing-driveitems?view=odsp-graph-online
• https://docs.microsoft.com/en-us/onedrive/developer/rest-api/concepts/addressing-driveitems?view=odsp-graph-online#net--c-sharp--visual-basic