Add object/filterValues and object/mapValues

[conradz]

This adds the object/filterValues() and object/mapValues() functions, which basically do the same thing as array/filter and array/map, except that they use objects instead of arrays.

The use case I had for this was converting a complex object into simple a JSON object, using filterValues() to remove unneeded values and mapValues() to convert to simpler JSON values.

[millermedeiros]

Nice, these methods are indeed useful.

What about naming it object/filter and object/map instead? I know it might sound confusing but in AMD we can give the local variables different names to avoid collisions so having different packages is enough to differ both:

define(['amd-utils/array/map', 'amd-utils/object/map'], function(arrMap, objMap){
  // ...
});

PS: we already have a math/map module and we will probably have other functions in different packages with similar names.

[conradz]

OK, done.

I knew that you could have the same names, but I didn't know if this was desirable. I guess the functions are almost identical except for using objects, so they probably should have the same name.