Bug fix: We want the records with better relevance first, so sort in descending order of the weightings.

Conflicts:
	lib/acts_as_indexed/class_methods.rb
Avoid a weighting of 0 when the matched records equals the total number of record

Conflicts:
	lib/acts_as_indexed/search_atom.rb
Review of results order in all tests, done before applying @phurni bug fixes, which fixed all issues.