Squashed commit of the following:

commit 8cb2b6307dcab737eb74bb4eaf1bbf94ac4dacb0
Author: Julius Pfrommer <julius.pfrommer@web.de>
Date:   Fri Jun 9 09:56:31 2017 +0200

    remove the header for external namespaces

commit a08052e9307e82701ba9c815d0fa6c9910fd9418
Author: FlorianPalm <palm@plt.rwth-aachen.de>
Date:   Fri Jun 9 09:16:04 2017 +0200

    removed all ifdefs related to UA_ENABLE_EXTERNAL_NAMESPACES

commit ea3c71824c7b4477428b261213e9a0a039c59080
Author: Julius Pfrommer <julius.pfrommer@web.de>
Date:   Thu Jun 1 10:14:20 2017 +0200

    fix #1509, link to the correct release files from the readme

commit aa717f20e2644ababd501f42712aa03aed2b93c6
Author: Julius Pfrommer <julius.pfrommer@web.de>
Date:   Sat May 27 19:03:06 2017 +0200

    always use thread_local globals; prevent nesting exchangeBuffer()

commit 945ea49d33cb3074de859a01626d9cbd86b2cacc
Author: Julius Pfrommer <julius.pfrommer@web.de>
Date:   Thu May 25 11:49:23 2017 +0200

    fix a case where the encoding buffer was not exchanged

commit 3fa676c08fa2dde7a0c2f773dfdaaa40d7c5e06c
Author: Bostjan Vesnicer <bostjan.vesnicer@gmail.com>
Date:   Thu May 25 08:54:48 2017 +0100

    Improve binary encoding/chunking tests
Merge branch '0.2'