update xonsh package

[eugenesvk]

Change tag version installation scheme to separate installs based on ST versions since ST updated its native Python syntax highlighting scheme to v2 since 4148+

• I'm the package's author and/or maintainer.
• I have have read the docs.
• I have tagged a release with a semver version number.
• My package repo has a description and a README describing what it's for and how to use it.
• My package doesn't add context menu entries. *
• ± My package doesn't add key bindings. **
  It overrides quotes '/" to add a nicety of autopair after "\b" in xonsh strings, so doesn't create any new key bindings
• (no commands) Any commands are available via the command palette.
• Preferences and keybindings (if any) are listed in the menu and the command palette, and open in split view.
  Don't think quote overrides need to be listed
• If my package is a syntax it doesn't also add a color scheme. ***
• If my package is a syntax it is named after the language it supports (without suffixes like "syntax" or "highlighting").
• I use .gitattributes to exclude files from the package: images, test files, sublime-project/workspace.

My package is a syntax highlighting package for the Python-powered shell xonsh (for files with .xsh and .xonshrc extensions)

[packagecontrol-bot]

Automated testing result: SUCCESS

Packages modified:
  - xonsh

[packagecontrol-bot]

Automated testing result: SUCCESS

Packages modified:
  - xonsh