Don't eat my ARGV!

Change the way that OptionParser.parse! is called, so that it doesn't
directly sink its teeth into ARGV.  This necessitated changing the way that
collect_command_line_tasks get the list of command-line arguments to examine
to get tasks and environment variable definitions, but that's a relatively
minor thing.
delete duplicated changelog line.
Merge pull request #10 from igrep/patch-1

delete duplicated changelog line.
Merge pull request #9 from mpalmer/dont-nuke-argv

Don't eat my ARGV!
Add #9 to History
Add #10 to History
Document handling of sentences in descriptions

Rake displays only up to the first sentence for `rake -T` and the entire
description for `rake -D` but this was not documented at Rake::DSL#desc.

Fixes #7
Skip testing default gems on rubies without them

Ruby 1.9.3 and earlier do not have default gems but Rake tests tried to
use them leading to an error.

Now the test using default gems is skipped when default gems are not
present.

Fixes #8
Set release version and date
backport r48409 from ruby trunk