Documentation on data_specs and spaces
Correct indentation in lists
Add missing characters
Replace :method: with :meth:
Merge pull request #1 from vdumoulin/lamblin-doc_data_specs

Fix sphinx syntax
"data set" -> "dataset"
Move to internal, fix "Python" to "python" in code-block
Move "big picture" earlier.
Merge pull request #408 from lamblin/doc_data_specs

Documentation on data_specs and spaces