RFR - Ma search buses

Both tests passing!
issue #43 
This is good, but this test will pass even if the search feature isn't working, because in the event of failure you're still displaying all the buses, so `bus.number` will appear on the page whether or not search works.

Instead, I'd create a number of buses (inside your `before :each`), some of which will meet the search criteria and others that won't.  Then test to make sure the ones that DO meet the search criteria are displayed, and the ones that DON'T aren't:

```ruby
    before :each do
      @matching_bus = FactoryGirl.create(:bus)
      @non_matching_buses = ["1", "20"].map do |line_no|
        FactoryGirl.create(:bus, number: line_no)
      end

      visit buses_path
    end

    scenario "user searches for valid search" do
      fill_in "search", with: @matching_bus.number
      click_button "Search"

      expect(page).to have_content(@matching_bus.number)

      @non_matching_buses.each do |bus|
        expect(page).to_not have_content(bus.number)
      end
    end
```

(Also, these tests are currently failing I think because a user needs to be signed in to search.  You may also need to use `flash.now[:notice] = "Could not find your search term"` in your controller action to make it appear.  If you want to display a flash notice within the same HTTP request cycle, you often have to use `.now` -- otherwise it won't show up until the next HTTP request is generated.)