RFC 2518 was removed because it is obsolete
RFC 4918 was added because it is actual
RFC 5689 was added because it updates RFC 4918

Wrapper script section was updated

Close #27

http.Do() method will return non-nil [error] in following cases:
1. Request is nil
2. Response missing Location header
3. Client failed to parse Location header
4. Method "request.GetBody()" returns error
5. Http.Client.Send() returns error
5. Client timeout was exceeded

Signed-off-by: Christoph Polcin <labs@polcin.de>

* method for creating parent collection was added to Client struct

"func (c *Client) createParentCollection(itemPath string) error" was added to request.go file

* using Client's method to create parent collection

in following methods:
Client.Write()
Client.WriteStream()
Client.copymove()

deadlock is impossible in method Client.copymove() because of paragraph #6 section 9.8.5 (https://tools.ietf.org/html/rfc4918#section-9.8.5) and paragraph #6 section 9.9.4 (https://tools.ietf.org/html/rfc4918#section-9.9.4) of RFC 4918 (https://tools.ietf.org/html/rfc4918)

* install dependencies script was added to Travis-CI file

* testing was added to Travis-CI file

* error wrapping was removed from Client.put() method

* using an early return on error in case of 409 in Client.Write() method

Digest authentication was improved

issue title: "Can't upload file with content"
https://github.com/studio-b12/gowebdav/issues/20

"opaque" field should not be specified if server did not provide it

"opaque" field should not be specified if server did not provide it

gitignore: .idea folder and *.exe files was added