title: rake db:migrate creates a development.sqlite3 file that is invalid
body: <p>I am learning ruby on rails following the Rails Tutorial by Michael Hartl.</p>
  
  <p>I am stuck in this issue that occurred when I ran bundle exec db:migrate, as expected, a development.sqlite3 file was created in my /db folder. </p>
  
  <p>So I tried to open that development.sqlite3 file using Sqlite Database Browser and it kept saying it was an invalid file. Tried to open it in other browsers and same thing... so apparently I am doing something wrong but cant find a workaround. </p>
  
  <p>Here are some hints that might help a more experienced developer find the cause.</p>
  
  <p>First of all I am using posgresql since thats what's recommended when you deploy on heroku. 
  My database.yml file looks like this:</p>
  
  <pre><code>development:
      adapter: postgresql
      encoding: unicode
      database: sampleapp_dev
      pool: 5
      username: *****
      password: *****
      min_messages: WARNING
      host: localhost
      port: ****
    test:
      adapter: postgresql
      encoding: unicode
      database: sampleapp_test
      pool: 5
      username: ****
      password: ****
      min_messages: WARNING
      host: localhost
      port: ****
    production:
      adapter: postgresql
      database: sampleapp_live
      username: ****
      password: ****
      host: localhost
      port: ****
  </code></pre>
  
  <p>This is what the console showed when I ran rake db:migrate</p>
  
  <pre><code>\sample_app&gt;bundle exec rake db:migrate
  
    ←[1m←[36mActiveRecord::SchemaMigration Load (1.0ms)←[0m  ←[1mSELECT "schema_mi
  grations".* FROM "schema_migrations"←[0m
  Migrating to CreateUsers (20140902194830)
    ←[1m←[35m (0.0ms)←[0m  BEGIN
  ==  CreateUsers: migrating ====================================================
  -- create_table(:users)
    ←[1m←[36m (159.1ms)←[0m  ←[1mCREATE TABLE "users" ("id" serial primary key, "n
  ame" character varying(255), "email" character varying(255), "created_at" timest
  amp, "updated_at" timestamp) ←[0m
     -&gt; 0.1601s
  ==  CreateUsers: migrated (0.1619s) ===========================================
  
    ←[1m←[35mSQL (3.0ms)←[0m  INSERT INTO "schema_migrations" ("version") VALUES (
  $1)  [["version", "20140902194830"]]
    ←[1m←[36m (17.7ms)←[0m  ←[1mCOMMIT←[0m
    ←[1m←[35mActiveRecord::SchemaMigration Load (1.0ms)←[0m  SELECT "schema_migrat
  ions".* FROM "schema_migrations"
  </code></pre>
  
  <p>I am pretty lost here, I dont see any errors, however when I try to open the .sqlite3 file to see that it has the columns I expect it to have, this message pops up: <strong>"Invalid File Format"</strong></p>
  
  <p>Has anyone had a similar issue or has an idea to solve this problem? </p>
  
  <p>Thank you so much!</p>