Tag MixedModels v0.2.5

I have deleted earlier versions of the package because I neglected to update the requirements to
```
julia 0.3-
```

I would appreciate it if a knowledgeable person could decide if that is going to cause havoc and, if so, ask me to create another pull request.  The situation I am worried about is the package being already installed then a 
```julia
Pkg.update()
```
finding that the currently installed version no longer exists and the currently available version cannot be installed because of its later requirements.