fix(example/startups): try using EnsureCreated to fix travis-ci build

failing with duplicate key value violates unique constraint "pg_database_datname_index"

Author: jaredcnance

src/JsonApiDotNetCoreExample/Startup.cs

@@ -63,7 +63,7 @@ public virtual void Configure(
             ILoggerFactory loggerFactory,
             AppDbContext context)
         {
-            context.Database.Migrate();
+            context.Database.EnsureCreated();
 
             loggerFactory.AddConsole(Config.GetSection("Logging"));
             loggerFactory.AddDebug();

src/NoEntityFrameworkExample/Startup.cs

@@ -54,7 +54,7 @@ public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerF
             loggerFactory.AddConsole(Configuration.GetSection("Logging"));
             loggerFactory.AddDebug();
 
-            context.Database.Migrate();
+            context.Database.EnsureCreated();
 
             app.UseMvc();
         }