Make binaries for download

[mathstuf]

I'd love to use this in my CI, but to use it, I'd need to do one of:

• add it to the main image in use (painful since I'm able to use vanilla rust:$ver containers now)
• add building cargo-sweep to my CI. This doesn't seem like it'd save me a lot of time (or ease of maintenance)

It'd be great if prebuilt binaries could be uploaded to the Releases page for use through a simple ( curl -O ... && verify && cargo sweep ) || :-like command chain in the CI script.

[tesuji]

cc #4

[Tarnadas]

Hey @holmgr,
apparently you did not properly generate your secure api key.
https://travis-ci.org/holmgr/cargo-sweep/jobs/489098782?utm_medium=notification&utm_source=github_status
Line 525 tells that api_key seems to be undefined. Can you retry generating the api key?
Also your latest tag is called v.0.5.0 which shouldn't have a '.' right after 'v'

[holmgr]

Hi @Tarnadas,
I generated a new tag/release v5.0.0.
Will try to generate a new API key :)