Recursively process files and allow individual file inputs

[sfraint]

Previously Netconan could only anonymize files in the root of the specified input directory.

This PR updates Netconan to:

• Allow individual files to be passed in for input and output
• Recursively process input directory

With a dir structure of:

anon/
configs/
    sensitive1/
        cisco.cfg
        juniper.cfg
    sensitive2/
        palo_alto.cfg

Now, the following is possible:

• netconan -i configs/sensitive1/cisco.cfg -o anon/cisco_anon.cfg -p -a
  • anonymizes only the cisco.cfg and saves it at anon/cisco_anon.cfg
• netconan -i configs -o anon -p -a
  • anonymizes and saves all three files under anon/, preserving original dir structure

Fixes https://github.com/intentionet/netconan/issues/60 and https://github.com/intentionet/netconan/issues/78

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This change is