For similarity corpora from in 0.2

Right now if we merge #8 

We will lose:
- [ ] SWSC
- [ ] WordSim353


Old code is at:

 - https://github.com/JuliaText/CorpusLoaders.jl/blob/65f349bbdf285fc3dda4139454e0b59079174ab9/src/similarity.jl

It needs porting to the new style
These are not traditional shaped corpora being for tasks.
Will need to think on best representation