Added ability for the archive option to be a function.

Closes gh-68.
v0.5.3
Remove verbose writeFlags as of Grunt v0.4.2 its automatic. Ref gruntjs/grunt#749.
Adding a note to 'archive' option to point out that it only applies to aggregate compression modes.
Moving 'archive' option doc changes to docs folder, which generates README.md.
Merge pull request #73 from TomGault/archiveOptionDocs

Adding a note to 'archive' option to point out that it only applies to aggregate compression modes.
Explicitly set files to publish to npm. Ref gruntjs/gruntjs.com#65