Return default paragraph definitions.

Defined values for paragraph start and separator doesn't seem to express
definition of code paragraph. Relying on comments doesn't work in all
situations. Default emacs paragraph definition provides safer common
definitions.
Merge pull request #24 from ap4y/fix_paragraph_movements

Return default paragraph definitions.
Add initial implementation of smie based indentation
Add more grammar rules for smie indentation
Add tests for all implemented smie grammars