kapitan refs fail to handle binary files

[ademariag]

Describe the bug/feature
Kapitan refs fail to correctly encode binary files, while it works ok with text files

To Reproduce
Steps to reproduce the behavior:

kapitan refs --write base64:binary/binary -t echo-server --base64 -f /usr/bin/true 
Traceback (most recent call last):
  File "/usr/local/bin/kapitan", line 8, in <module>
    sys.exit(main())
  File "/Users/ademaria/Library/Python/3.9/lib/python/site-packages/kapitan/cli.py", line 562, in main
    args.func(args)
  File "/Users/ademaria/Library/Python/3.9/lib/python/site-packages/kapitan/refs/cmd_parser.py", line 27, in handle_refs_command
    ref_write(args, ref_controller)
  File "/Users/ademaria/Library/Python/3.9/lib/python/site-packages/kapitan/refs/cmd_parser.py", line 50, in ref_write
    data = fp.read()
  File "/usr/local/Cellar/python@3.9/3.9.7_1/Frameworks/Python.framework/Versions/3.9/lib/python3.9/codecs.py", line 322, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xca in position 0: invalid continuation byte

Expected behavior
Binary is correctly encoded.

Screenshots
If applicable, add screenshots to help explain your problem/idea.

** If it's a bug (please complete the following information):**

• python3 --version: Python 3.9.7
• pip3 --version: pip 21.2.4 from /usr/local/lib/python3.9/site-packages/pip (python 3.9)
• Are you using pyenv or virtualenv? no

Additional context
Related to work for kapicorp/kapitan-reference#106

WORKAROUND
Simply encode the file before importing. i.e.:

base64 /usr/bin/true  | kapitan refs --write base64:binary/binary -t echo-server -f -