Restructure repo and update podspec

Author: morganchen12

GeoFire.podspec

@@ -1,27 +1,25 @@
 Pod::Spec.new do |s|
   s.name         = "GeoFire"
-  s.version      = "4.0.2"
+  s.version      = "4.1.0"
   s.summary      = "Realtime location queries with Firebase."
   s.homepage     = "https://github.com/firebase/geofire-objc"
   s.license      = { :type => 'MIT', :file => 'LICENSE' }
   s.author       = "Firebase"
   s.source       = { :git => "https://github.com/firebase/geofire-objc.git", :tag => 'v' + s.version.to_s }
-  s.source_files = "GeoFire/**/*.{h,m}"
-  s.documentation_url   = "https://geofire-ios.firebaseapp.com/docs/"
   s.ios.deployment_target = '10.0'
-  s.ios.dependency  'Firebase/Database', '~> 7.8.0'
-  s.frameworks   = 'CoreLocation', 'FirebaseDatabase'
   s.requires_arc = true
-  s.static_framework = true
+  s.default_subspec = 'Database'
+
+  s.subspec 'Database' do |db|
+    db.ios.dependency 'Firebase/Database', '~> 7.8.0'
+    db.ios.dependency 'GeoFire/Utils'
+    db.public_header_files = "GeoFire/API/*.h"
+    db.source_files = "GeoFire/Implementation/*.{hm}"
+    db.frameworks = 'FirebaseDatabase'
+  end
 
   s.subspec 'Utils' do |utils|
-    utils.source_files = [
-      "GeoFire/**/GFUtils*.[mh]",
-      "GeoFire/**/GFGeoQueryBounds*.[mh]",
-      "GeoFire/**/GFGeoHashQuery*.[mh]",
-      "GeoFire/**/GFGeoHash*.[mh]",
-      "GeoFire/**/GFBase32Utils*.[mh]",
-    ]
+    utils.source_files = "GeoFire/Utils/*.{hm}"
     utils.frameworks = 'CoreLocation'
   end
 end