make sure nil isn't memoized and frozen

We shouldn't try to rescue every type of exception here

Dup string before changing encoding because it might be frozen

Calling String#force_encoding! on a frozen string throws an exception.
By dupping the string we prevent this from happening.

[2.3] Kill Object#` monkey patch

CVE-2014-0081

Removes the X-Runtime header from ActionController::Benchmarking

The `Rack::Runtime` middleware now provides this header

Backport Rack session skip

Builder 3.2.2

i18n 0.4.1

Don't run tests on 1.9.3

Disable auto-generated form field IDs by passing nil for "id" attribute

Previously it was not possible to opt out of auto-generated ID values
for various form fields.

Freeze ERB string literals

Fix fragment caching in mixed encoding scenario