Use Alpine Linux for Docker Builds

[gthole]

Hello! Exploring euterpe and considering the possibility of adopting it for my personal music server. I thought I'd contribute a small change in return.

I suggest switching to alpine linux in the Dockerfile.

This results in:

• Smaller image sizes
• More secure application environment
• Only use packages required for build

Thanks so much!

[coveralls]

Pull Request Test Coverage Report for Build 1641203785

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 8 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.2%) to 80.858%

---

Files with Coverage Reduction	New Missed Lines	%
src/library/database.go	4	78.95%
src/library/local_library.go	4	77.47%

Totals
Change from base Build 1377746862:	-0.2%
Covered Lines:	3109
Relevant Lines:	3845

---

💛 - Coveralls

[ironsmile]

Good idea, thank you! I too prefer Alpine lately and it is only inertia which kept Debian in play here.

[ironsmile]

Thank you for the suggestion! ♥ It has been added to master already with 32ce53d and 22f9aed. I am closing this PR.

On the next release the published Docker hub image will be using Alpine 🎉