Version 0.3.1 of getopt.net

As per issue #8 from @DanStale, getopt.net did not behave correctly w…

…hen certain options were added to ShortOpts and non-option arguments were passed to the library.

**Changes**
 - Added check to determine whether 0x01 must be returned, depending on whether or not ShortOpts[0] == '-'.
 - Added check to determine if parsing should stop, depending on whether or not ShortOpts[0] == '+'.
 - If IgnoreInvalidOptions is true and MustReturnChar1() returns true, then NonOptChar is returned.
 - Previously private consts are now public
 - If a non-option string is encountered and IgnoreInvalidOptions is true, outOptArg is set to the value of the non-option string.
 - Updated and refactored MSTests
 - Corrected false behavior where encountering "--" would immediately stop GetNextOpt
   - the correct behavior is to simply stop parsing options, but still return 0x01 and outOptArg contains the value of the argument passed
 - bumped up library version

**Issues fixed**
This PR fixes #8.

**New library version**
The new version for the library is now 0.3.0

Version 0.2.0 beta

The very first version of getopt.net by Simon Cahill!

This is a fully-functioning beta.
The contents of the beta are subject to change!