Don't require image bin deps till necessary

Related to gh-123
Update package.json
Merge pull request #125 from nschonni/lazy-require-deps

Don't require image bin deps till necessary
update deps
add time-grunt to make sure we don't regress in speed
0.4.1
changelog
Rewrite
Merge pull request #97 from kevva/refactor

Rewrite
minor tweaks
0.5.0
changelog
Update package.json
Update .travis.yml
Squashed commit of the following:

commit b22ba03a76cb7a5f666d97c68b621dbb0db5701a
Author: Catherine Farman <cfarman@gmail.com>
Date:   Tue Feb 18 13:29:41 2014 -0800

    Update dynamically mapped files link

    documentation has moved from Github to gruntjs.com for this link.

Closes gh-156.
Fix docs 404
Merge remote-tracking branch 'upstream/master'

Conflicts:
	tasks/imagemin.js