switch to shorter format for shrinkwrap file

instead of list of component object with version and name we now have a
single dependencies object - this is the same format that is used in
package.json and component.json

old format is still being supported, it's read and processed
automatically and can be save if '--long' options is passed
add --check option when saving the shrinkwrap file

if check is enabled we will verify if packages can be re-installed
reliably and warn if problems are found

There are 2 kind of problems that can be detected.
- version in component.json file is not the same as tagged version - in
  which case we just warn the user
- version in component.json is not tagged at all - in which case we set
  it to '*' in shrinkwrap file which causes master to be installed

In both cases the best course of action is to notify the component owner
and ask the components to be properly tagged.
Merge branch 'deps-format'
Merge branch 'verify'
Release 0.6.0