Gemfile & gemspec maintenance

It introduces the following changes:

* Remove unused and unnecessary dependencies
* Install database adapter based on DB ENV variable
* Move sqlite adapter to gemspec and lock it to version 1.3

Author: aitbw

Gemfile

@@ -3,16 +3,12 @@ source "https://rubygems.org"
 branch = ENV.fetch('SOLIDUS_BRANCH', 'master')
 gem "solidus", github: "solidusio/solidus", branch: branch
 
-if branch == 'master' || branch >= "v2.0"
-  gem "rails-controller-testing", group: :test
+if ENV['DB'] == 'mysql'
+  gem 'mysql2', '~> 0.4.10'
 else
-  gem "rails_test_params_backport", group: :test
+  gem 'pg', '~> 0.21'
 end
 
-gem 'pg', '~> 0.21'
-gem 'sqlite3'
-gem 'mysql2', '~> 0.4.10'
-
 group :development, :test do
   gem "pry-rails"
   gem 'i18n-tasks', '~> 0.9' if branch == 'master'

solidus_i18n.gemspec

@@ -27,4 +27,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rubocop', '>= 0.24.1'
   s.add_development_dependency 'rspec-rails', '~> 3.1'
   s.add_development_dependency 'simplecov', '~> 0.9'
+  s.add_development_dependency 'sqlite3', '~> 1.3.6'
 end