No support for custom dict geration

[Enzodtz]

Hey,

Right now, the GeneratorFromDict doesn't have support for using a custom dict, it only uses the language one.

This is bad, since when generating data, you probably would like to use lots of strings, and its not good to put code together with that list.

You can of course load the dict by yourself but use the string generator, but that doesn't seem that convenient.

I'll be happy to work to allow this feature :)

[Enzodtz]

I've openned a PR that fix this issue: #249