bump version to ios-v3.0.0-pre.8

[skip ci]

ios/Mapbox-iOS-SDK.podspec

@@ -1,7 +1,7 @@
 Pod::Spec.new do |m|
 
   m.name    = 'Mapbox-iOS-SDK'
-  m.version = '3.0.0-pre.7-symbols'
+  m.version = '3.0.0-pre.8-symbols'
 
   m.summary          = 'Open source vector map solution for iOS with full styling capabilities.'
   m.description      = 'Open source OpenGL-based vector map solution for iOS with full styling capabilities and Cocoa bindings.'

platform/ios/MGLAccountManager.m

@@ -85,7 +85,7 @@
 }
 
 + (NSString *)kitDisplayVersion {
-    return @"3.0.0-pre.7";
+    return @"3.0.0-pre.8";
 }
 
 + (void)initializeIfNeeded {