Support for search, child pages enumeration, content creation & ancestors

[gm42]

It also contains fixes for the usage of new/update.

[jesselang]

Hey @gm42! Thanks for these contributions. FWIW, I created #3 with your changes to start the discussion around getting them merged. However, @seppestas had some concerns here: https://github.com/seppestas/go-confluence/pull/3#issuecomment-333125154 I massaged your changes into smaller logical sets, and submitted the first one as #9, as well as merged them into my fork (https://github.com/jesselang/go-confluence/pull/2, https://github.com/jesselang/go-confluence/pull/3, https://github.com/jesselang/go-confluence/pull/4, and https://github.com/jesselang/go-confluence/pull/5). I hope you don't mind. I believe there is more work to be done in regard to exposing the response body when errors occur, but I wanted to address that as a separate set of changes.