Document argument parsing change in test

[robbiegill]

There were explicit changes in argument parsing behavior since 10.1.1, but there also seems to be some undocumented changes in handling of some parameters. I actually think the new behavior is more sane, so here's a pr to document the current behavior in tests.

In 10.1.1, 'empty' args were not included in the arg array returned from parse_task_string. In 10.3.2 'empty' args are pass as empty string.

#10.3.2
name, args = @app.parse_task_string("name[one,]") 

name # => 'name'
args # => ['one', '']

#10.1.1
name, args = @app.parse_task_string("name[one,]") 

name # => 'name'
args # => ['one']

[hsbt]

@robbiegill Hi, I merged your pull request on new canonical repository as ruby/rake.

see. https://github.com/ruby/rake/commit/da1c4136748e55fbe99b16130040b5f302db375c

[robbiegill]

Thanks! Closing this pr.