2.6.6 release (#134)

* 2.6.7 release

* Update CMakeLists.txt

use 2.6.6

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Co-authored-by: Simon Pintarelli <[email protected]>

remove tar.gz deps on release

Creating a tar.gz containing the dependencies is obsolete. The current cmake
checks explicitly for git submodule and otherwise attempts to find external
packages.

Version bump

update version to 2.6.2 in cmake

Updated submodules.

Fixed a bug with memory pool resizing.

Update .gitattributes

Updated the version in CMakeLists.txt

Updated README, ATTRIBUTIONS and the version.