Support Build on various OS's and fix vulnerabilities

[gabefair]

Node install now works on the following tested operating systems:

1. Windows 10 x64
2. WSL Ubuntu 18.10 x64
3. Mac High Sierra x64
4. Ubuntu Desktop 16.04 x64
5. Ubuntu Server 18.04 ARM

Weirdly, chissl utility functions in python-chissl/chissl/util were not being seen during python import. Various methods were tried but different results would happen on different os's.
Finally what worked was removing the util folder and adding the following code to the server.py file:

if __package__ is None or __package__ == '':
    # uses current directory visibility
    import chissl_mongo as cm
else:
    # uses current package visibility
    from . import chissl_mongo as cm