Removing zlib1g, libssl-dev, cryptopp, and expat.
Cryptography now uses public domain code in the source tree (source/detail/cryptography), zlib was replaced with miniz and added to the source tree (source/detail/serialization/miniz.*), and since it's already a part of libstudxml (i.e. a grandchild dependency), xlnt is now using libstudxml's expat (third-party/libstudxml/xml/details/expat).
Removing the -I and -L arguments from the compile command.
I realize that it is unnecessary to specify a list of directories (to be searched) for header files and so forth in the event that the standard xlnt installation process was followed.
Adding the future steps in readiness; waiting for the gcc 6.3.0 to compile - boy that takes a while.
Next step is to run everything after the TODO line and the create a pull request to finalize the documentation
