Investigate improvements to duplicate searching

[smarziano]

This relates closely to issue #179. @shua123 has implemented some duplicate checks for the recent sign-up process with commit 7a7ff8b. However, we will need to refine the address duplicate check because addresses can be the same but be entered differently (1234 West Belmont Ave vs. 1234 W Belmont are the same address). There is no fuzzy duplicate checking happening and we want to investigate options.