Version 2.0.0

• Updated language core update --dry-run message [#32]
• Update scaffolded files [#34]
• Add is-installed command to check if a given language is installed [#36]
• Add language plugin and language theme command. [#29]
• Warn if no plugin or theme has been specified [#38]
• Use download_url() in language pack upgrader [#41]
• Enable updating languages for individual plugins and themes [#40]
• Adapt package for framework v2 [#43]