Modify search funtions in Engine::Linux
Modify search funtions in Engine::Linux

InsensitiveSearch::Engine::Linux
----

- #search
  - Move the process to split path_source into #search_start.
  - Pass its argument to #search_start.
- #search_start
  - Change the argument.
  - Add the process to split path_source.
  - Fix YARD comment.

indeep-xyz/ruby-insensitive-search,indeep-xyz/ruby-insensitive-search