Set up Travis to upload binary for every release

[matematikaadit]

• Add deploy script
• Set deployment option on .travis.yml

fix #76

Example of it in action
https://github.com/matematikaadit/fd/releases/tag/v5.0.0-rc2

It will upload:

• fd-VERSION-i686-unknown-linux-gnu.tar.gz
• fd-VERSION-i686-unknown-linux-musl.tar.gz
• fd-VERSION-x86_64-apple-darwin.tar.gz
• fd-VERSION-x86_64-unknown-linux-gnu.tar.gz
• fd-VERSION-x86_64-unknown-linux-musl.tar.gz

With the content of the archive:

• fd-VERSION-TARGET/
• fd-VERSION-TARGET/LICENSE-APACHE
• fd-VERSION-TARGET/LICENSE-MIT
• fd-VERSION-TARGET/README.md
• fd-VERSION-TARGET/autocomplete
• fd-VERSION-TARGET/autocomplete/_fd
• fd-VERSION-TARGET/autocomplete/fd.bash-completion
• fd-VERSION-TARGET/autocomplete/fd.fish
• fd-VERSION-TARGET/fd
• fd-VERSION-TARGET/fd.1

[matematikaadit]

I should mentions that this commit is using secret key for my repo, and should be updated accordingly. Instruction on how to update are included in the comments:

  # NOTE updating the `api_key.secure`
  # - go to: https://github.com/settings/tokens/new
  # - generate new token using `public_repo` scope
  # - encrypt it using: `travis encrypt API_KEY_HERE`
  # - paste the output below
  api_key:
    secure: ...

[sharkdp]

Thank you very much! This is fantastic and will save us a lot of time.

I'll update the secret key after merging this.