CMake config does not work

I am willing to help you with this bug, but I want to check out other parts of the UI and work on specific items. Taking over the world. Haha.

Here are the pros of using CMake:
  -has a fully working configure-like framework, that is easy to use
  -has no other dependencies except for a C++ compiler
  -supports basically every UNIX, MS Windows (MSVC, Borland, cygwin, mingw) and Mac OS X
  -has a simple syntax
  -features a testing framework

That's quite some pros! So you could get this working? That would be awesome.

PS: I would be happy with some help. I have never used Vala or Gtk, so I have to do much research, slowing down the whole process, and probably still doing some things wrong :). I'd be happy with your contributions!

It was happening to me too, in order to make it work you just need to do:

sudo apt-get build-dep scratch-text-editor

I had this same problem. It came from the instructions on the getting started page https://elementary.io/docs/code/getting-started#bazaar, where it says to copy the folder cmake over to hello-again. It actually meant copy cmake's contents over to hello-again. I did this and got it to run

I was also following https://elementary.io/docs/code/getting-started#bazaar and had the same problem. What's happening is that the compiler needs a folder where it can find the Vala files it needs. The message says:

By not providing "FindVala.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "Vala", but
  CMake did not find one.

The "FindVala.cmake" file was in cmake-modules/src (in my case, you'd need to find out how that works for you), so I opened up my CMakeLists.txt in my app's root folder and added this to it's fourth line:

list (APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake-modules/src)

After that I could configure and build everything.

Just to make it clear, the first lines of my hello-world's CMakeLists.txt now look like this:

project (hello-again)
cmake_minimum_required (VERSION 2.6)
list (APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake-modules)
list (APPEND CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake-modules/src)
set (DATADIR "${CMAKE_INSTALL_PREFIX}/share")

Tommy's suggestion also worked for me, but then the cmake and my app files got all mixed up... if that was confusing for a hello world app I wonder what would happen in an actual project. lol

If you want to push a branch, I would be more than happy to accept any
improvements.

Thanks Yuri Witte and all the guys! it worked finally!