Linux AArch64 wheels

Updated channel write functions, added channel write tests. (Parallel…

…SSH#36)

* Updated channel write functions, added channel write tests.
* Updated appveyor cfg
* Updated changelog, docstrings

Updated changelog, readme, rtd configuration (ParallelSSH#32)

* Updated changelog, readme, rtd configuration
* Updated setup.py, key C file
* Updated manylinux scripts, docker file, krb archive and openssl version.
* Updated manylinux binary wheel openssl to 1.1
* Lfs track xz
* Updated embedded openssh test server

updated circleci cfg (ParallelSSH#33)

* updated circleci cfg

Timeout tests (ParallelSSH#28)

* Raise error when failing to create new channel object. 
* Added timeout settings tests.
* Added check for new local libssh install dir. Updated gitignore.
* Updated manifest
* Updated changelog

Updated appveyor cfg (ParallelSSH#29)

Gss api delegate (ParallelSSH#22)

Updated changelog.
Added function for setting GSS API delegation option on session. Added GSSAPI authentication tests.
Updated import privkey function signatures.
Added agent authentication test. Updated import privkey functions to default to empty passphrase.

Channel dealloc (ParallelSSH#19)

Fixed issue with channel double free when session open channel fails.
Updated exception handling for session authentication.
Updated tests.
Removed unused exceptions.
Added documentation.
Updated readme, changelog.

OSX and Windows wheels (ParallelSSH#18)

Added OSX wheel builds for 10.14 and 10.15 on Py3.8
Added Windows wheel builds for Python 3.6/3.7/3.8

Added sdist upload (ParallelSSH#13)