Add support for setting custom lxc-start arguments from Vagrantfile

Useful for #10

example/Vagrantfile

@@ -8,6 +8,7 @@ Vagrant.configure("2") do |config|
   config.vm.hostname = 'ubuntu-cloud-box'
 
   config.vm.provider :lxc do |lxc|
-    # ... soon to come lxc configs...
+    lxc.start_opts << 'lxc.cgroup.memory.limit_in_bytes=400M'
+    lxc.start_opts << 'lxc.cgroup.memory.memsw.limit_in_bytes=500M'
   end
 end

lib/vagrant-lxc/action/boot.rb

@@ -3,7 +3,8 @@ module Vagrant
     module Action
       class Boot < BaseAction
         def call(env)
-          env[:machine].provider.container.start
+          config = env[:machine].provider_config
+          env[:machine].provider.container.start(config)
           @app.call env
         end
       end

lib/vagrant-lxc/config.rb

@@ -1,6 +1,14 @@
 module Vagrant
   module LXC
     class Config < Vagrant.plugin("2", :config)
+      # An array of options to be passed to lxc-start when booting the machine.
+      #
+      # @return [Array]
+      attr_reader :start_opts
+
+      def initialize
+        @start_opts = []
+      end
     end
   end
 end

lib/vagrant-lxc/container.rb

@@ -66,8 +66,10 @@ module Vagrant
         end
       end
 
-      def start
-        lxc :start, '-d', '--name', @name
+      def start(config)
+        # @logger.info('Starting container...')
+        opts = config.start_opts.map { |opt| ["-s", opt] }.flatten
+        lxc :start, '-d', '--name', @name, *opts
         wait_until :running
       end
 

spec/unit/container_spec.rb

@@ -139,18 +139,21 @@ describe Vagrant::LXC::Container do
   end
 
   describe 'start' do
-    let(:name) { 'container-name' }
+    let(:config) { mock(:config, start_opts: ['a=1', 'b=2']) }
+    let(:name)   { 'container-name' }
 
     before do
       subject.stub(lxc: true, wait_until: true)
-      subject.start
+      subject.start(config)
     end
 
     it 'calls lxc-start with the right arguments' do
       subject.should have_received(:lxc).with(
         :start,
         '-d',
-        '--name', name
+        '--name', name,
+        '-s', 'a=1',
+        '-s', 'b=2'
       )
     end