Finder search *only* searches file-names (Macbook Air, El Capitan)
Solution:

Navigate to System Preferences>Keyboard>Shortcuts>App Shortcuts

Press the 'plus' (add) button

In Application, choose Finder

For Menu Title, enter "Find by Name…"  Do not use the "" and you must use an ellipsis (…), not three periods (...).

Enter your desired keyboard shortcut.  I use CMD-F, replacing the default behavior of regular Find.  I then repeated the process, adding a keyboard shortcut the the Finder of CMD-OPT-F for Find.