Algernon 1.15.2

• Remove a duplicate word from the README.md file (thanks Philipp Gillé / @philippgille).
• Serve Algernon web applications (.alg files) from memory if /dev/shm is writable, ref #132 (thanks Dialga / @Dialga).
• Switch from github.com/xyproto/env to github.com/xyproto/env/v2.
• Serve .json files a tiny bit faster.
• Update dependencies.