update changelog
store in sorted form
Make sure there aren't multiple solutions in the resolve tests
Don't install a package with a feature unless it is explicitly requested

This will prevent mkl versions of numpy, scipy, etc. from slipping in when
they weren't asked for.

In general, the use-cases we have in mind for features are such that they
shouldn't be installed unless they are specifically requested.

Fixes #629.
Merge branch 'master' of github.com:conda/conda
Update the CHANGELOG
put new history module into action
remove unused code
add ability to show channel URLs when displaying download preview
add comment
add urls to cache
Merge branch 'master' into depsnotfound

Conflicts:
	conda/resolve.py