Add support for command-line options with '+' prefix
Add support for command-line options with '+' prefix

Example:

    dig example.com +short +time=3
    #               ^ punctuation.definition.command-switch.shell
    #               ^^^^^^ support.command-switch.shell
    #                      ^ punctuation.definition.command-switch.shell
    #                      ^^^^^ support.command-switch.shell
    #                           ^ keyword.operator.assign.shell

jfcherng/Sublime-ShellScriptImproved