Restrict sqlite3 gem to '~> 1.3', like ActiveRecord

They just released sqlite3 2.0.0, but ActiveRecord's sqlite3 adapter
doesn't know about this yet, leading to conflicting sqlite3 gems in
specs.

This is probably a temporary fix until ActiveRecord learns the news.

Gemfile

@@ -19,6 +19,7 @@ dbs = ENV['DB_ALL'] ? 'all' : ENV.fetch('DB', 'sqlite')
 gem 'mysql2', '~> 0.5.0', require: false if dbs.match?(/all|mysql/)
 gem 'pg', '~> 1.0', require: false if dbs.match?(/all|postgres/)
 gem 'fast_sqlite', require: false if dbs.match?(/all|sqlite/)
+gem 'sqlite3', '~> 1.4', require: false if dbs.match?(/all|sqlite/)
 
 gem 'database_cleaner', '~> 2.0', require: false
 gem 'rspec-activemodel-mocks', '~> 1.1', require: false