Makefile to simplify multifile gists

[miraculixx]

gist is a great tool, thanks for making it

I would like to contribute this small utility to simplify multi-file gists
https://gist.github.com/miraculixx/65b3f3f57f1c2c7d339331ffd8f87e4f

# makefile to simplify use of gist for multi-file gists
#
# Usage:
#    1. create a .gistignore file with file patterns to ignore
#    2. make gist
#
#       this will create/update the gist including all files not matched by any
#       pattern in .gitignore. The URL will be printed and stored in .gist
#
#    3. make clean
#
#       this will delete the gist