Clarify project dependencies.

As requested in issue #60.
Also remove broken builds, pending replacement.
no-tn-check

Change-Id: I44158cef8a301e710300dbaf7174ee270846f711

Author: t-14

README.md

@@ -7,18 +7,15 @@ documentation in the `docs/` directory.
 Code status
 ===========
 
-Build status with GNAT GPL 2017
-
-Platform | Status
----------|-------
-Linux    | [![Build Status](https://travis-ci.org/AdaCore/gnatcoll-core.svg?branch=master)](https://travis-ci.org/AdaCore/gnatcoll-core)
-Windows  | [![Build status](https://ci.appveyor.com/api/projects/status/31a7dh523xto7b9f/branch/master?svg=true)](https://ci.appveyor.com/project/github-integration-adacore/gnatcoll-core/branch/master)
+TBD
 
 Dependencies
 ------------
 
-GNATCOLL only depends on a recent GNAT compiler. Building it also requires
-GPRbuild.
+GNATCOLL requires a recent GNAT compiler. Building it also requires
+GPRbuild. GNATCOLL.Projects depends on LIBGPR library which is bundled with
+the GNAT installations provided by AdaCore, and is otherwise part of
+GPRbuild project.
 
 Configuring the build process
 -----------------------------