creates chunk table

- chunks have many projects, projects have many chunks
- chunks have a type field in order to support single table inheritance.
adds SLI children. associations not currently working
adds children fields to chunks table.
SLI basic set up

projects have many chunks, and chunks can either be images, codesnippets, or describers (e.g. all text). query interface supports all model names.
Chunks now can be created with different attributes, depending on their type.

- chunks controller now deals with different cases for different children.

- all  children tables set their inheritance column to nil, in order to facilliate a parent controller create.

- new create route made

- more fields added to chunk table, now reflected in schema and models.
remove references to code snippet project attribute. functionality will eventially be replaced by chunks
remove code snippet from new/edit projects form
chunks views now exist
merge conflict less conflicted

- project model now has a number valdation, and associations with chunks
- project mode spec is consequently updated

Merge branch 'master' of https://github.com/dmill/gitfolio into chunk-builder

Conflicts:
	app/models/project.rb
	spec/models/project_model_spec.rb
Merge pull request #46 from dmill/chunk-builder

Chunk builder