Move to "Address or Zip Code" Entry

[subdigital]

We've received a bunch of reports that niether zip code nor GPS provide 100% functionality with respect to congressional districts. We need to allow passing a full address to the API in these cases.

• Remove zip code validation
• make text field read "Enter Zip or Address"
• update any references to zip code (we can just call this an "address" in the code)
• URL encode whatever they type and pass to API in FetchIssuesOperation
• update any alert dialog messaging about split districts to reflect this

[subdigital]

@tomburns is working on this.

[tomburns]

Welp, just noticed this :) I'll update the UI text in my PR

[tomburns]

@subdigital I think this issue can be closed after PR #106