Regenerate and reload any imported files.

In some cases, loading an imported file will modify the task that
generates that file.  However, since that task was already invoked
prior to the import, it will not be re-invoked.  This can result in
the imported file never being re-generated.
Make Task#source default to the first prerequisite in non-rule tasks.
Better rake task argument parser that accepts commas in argument values
Make #sources a synonym for #prerequisites if @sources isn't set.

I've opted for a pretty conservative definition of this - `#sources`
will prefer to return `@sources` even if `@sources` is set to `nil`
Fix rake.1.gz. It was corrupted.
Fix a test failure on Windows

test-all on ruby repository fails because the path doesn't have a
drive letter on Windows. Rake::Backtrace.collapse also uses
File.expand_path internally to make suppressed paths.
Completed namespaced task definitions

Tests include working within another namespace, and that the TM scope isn't
clobbered
Made a correction to the documentation, explaining how to call tasks with arguments when the arguments contain spaces
Updated Gem::Specification to require Ruby >= 1.9
fix typo at https://github.com/ruby/ruby/pull/500
Clarify rake -f usage.

Users that are used to make semantics might not expect,
that parent directories are still being searched.
Add build_all capability.
Update rakefile.rdoc
Merge pull request #256 from valera-rozuvan/patch-1

Fix typo in rakefile.rdoc
Track future history in History.rdoc

Mention #256 in History
Merge pull request #252 from mpfz0r/master

Clarify rake -f usage.
Add #252 to History
Add #251 to History
Merge pull request #250 from hsbt/fix-typo

Fix typo. From ruby/ruby#500
Merge pull request #247 from parndt/patch-1

Updated Gem::Specification to require Ruby >= 1.9