Ast branch fix after gem name changed to bb_gun

Conflicts:
	lib/bb_gun.rb
	lib/bb_gun/ast.rb
	lib/bb_gun/ast_spec.rb
	lib/bb_gun/node.rb
	lib/bb_gun/tag.rb
	spec/bb_gun/ast_tree_spec.rb
	spec/bb_gun/node_spec.rb
basic structcure for ast and text elements array

I created classes needed for AST, but building tree is not working yet.
For now, there is method for creating array with text divided
to elements which will be later processed.
simplifying AST