Fix custom_namespace synchronization issues

* do not modify class variables when rendering form
* use options to pass custom namespace
* do not interfere with `fields_for` :namespace option
* introduce builder.dom_id_namespace (because thats what it actually is)
fix case when parent builder is self
fix CHANGELOG

#1025 removed the `:value` option, not the `:input_html => { :value => '...'}` option
remove rails < 3.1 stylesheet doc from readme

rails < 3.2 is deprecated, old assed installation is no longer needed
Merge pull request #1067 from timoschilling/patch-2

remove rails < 3.1 stylesheet doc from readme
Merge pull request #1066 from timoschilling/patch-1

fix CHANGELOG for value option
add ROADMAP file to track deprecations
rename to DEPRECATIONS
Merge pull request #1068 from justinfrench/roadmap

Add DEPRECATIONS file
Merge pull request #1065 from mikz/fix-custom-namespace

Fix custom_namespace synchronization issues
Merge remote-tracking branch 'upstream/master' into configurable-namespaced-inputs