Ability to get data about all projects

Hello,

I have added ability to get data about all available projects.
Data are accessible by the following URL:
http://spmjs.io/repositories/
It is possible to apply filter for project names and specify which fields should be included into project’s data. For example:
http://spmjs.io/repositories/?projects=imagic,mixing,kemo,madge&fields=name,description,keywords,license,version
Moreover if you approve adding [minimatch](https://github.com/isaacs/minimatch) or [gex](https://github.com/rjrodger/gex) as dependency I will improve filtering so that it will possible to specify projects or fields by pattern.