# v0.5.10
    * Fixed bug when the only options available have no long version in help info
# v0.5.9
    * Removed unstable features for Rust 1.0
    * Removed libc as a dependency in favor of std::process::exit()
# v0.5.8
    * Fixed bug with positional arguments who are required by others, but not listed in usage
    * Improved error messages for arguments with exclusions
    * Fixed help information formatting (regression from a rebase)
    * Improved assertions for flag arguments
    * Small code clean ups
# v0.5.7
    * Fixed bug with required-by-default arguments who are mutually exclusive
      with matched arguments
# v0.5.6
    * Fixed another bug in help info formatting, help info is now 100%
# v0.5.5
    * Fixed formatting in help info when flags or options have a long but no short
    * Prefer long in usage info when a required option has both long and short
# v0.5.4
    * Positional arguments that accept multiple values are now displayed correctly
      in usage and help string with '...' indicating multiple values
# v0.5.3
    * Added support for positional arguments which accept multiple values if they
      are last (i.e. have the highest index)
    * Fixed several assertions for developer errors (i.e. not end-user errors)
# v0.5.2
    * Fixed a bug when applications have hyphens in their names
# v0.5.1
    * Fixed a bug when the only arguments you've defined are also required
# v0.5.0
    * Added support for values and positional arguments with only specific values
    * Some performance fixes
    * Minor bug fixes
# v0.4.18
    * Correctly displays subcommand names when printint help, version, or usage
      (i.e. 'parent-subcommand' for help/version or 'parent subcommand' for usage)
    * Fixed bug with arguments required by other arguments, not displaying as
      required to the user when printing usage information
    * Changed some format!() to .to_owned() for performance reasons
# v0.4.17
    * Arg values now accept lifetimes other than 'static
# v0.4.16
    * Fixed bug with multiple options
    * Removed unneeded Box<>'s
    * Fixed formatting with positionals in help info
# v0.4.15
    * Changed libc to crates.io in prep for Rust 1.0 stability
# v0.4.14
    * Changed App version, about, name, author, and usage to allow lifetimes other than 'static
# v0.4.13
    * Bug fixes with how multiple options are parsed
# v0.4.12
    * Minor bug fixes
# v0.4.11
    * Bug fixes and cleaned up code organization (well started to...)
    * Changed runtime representation of arguments to lower allocated memory
# v0.4.10
    * Minor bug fixes
    * Added more comprehensive examples to repo