75 setup

solves #75, apart from configuration block (still has to be written)
tries to solve #76 
README.md changed quite a lot and can be tested with ataru
This code joins filepaths as if they were strings. This can lead to subtle bugs, e.g.:

```ruby
"foo/" + "/bar" #=> "foo//bar"
```

The better option is:

```ruby
File.join(path1, path2)
```
Which does the right thing  (tm) and describes what you are (joining filepaths).