add hostname to layout directives
more idiomatic hostname lookup, ensuring UTF-8 encoding for YAML generation
Merge branch 'master' of https://github.com/bisceglie/logging into bisceglie-master

* 'master' of https://github.com/bisceglie/logging:
  more idiomatic hostname lookup, ensuring UTF-8 encoding for YAML generation
  add hostname to layout directives
Retrieve the hostname only once when the layout class is first loaded.