This commit also implements a faster version of #demodulize I was unable
to isolate with git add --patch.

Not a big fan of the name #deconstantize. It complements #demodulize
getting rid of the rightmost constant, hence the name, but it is
unrelated to the well-known #constantize. So unsure. Could not come
with anything better, please feel free to rename.

removed reference to SynchronizedMemoryStore and CompressedMemCacheStore (the remaining code from 9cafc288)

This is also faster on 1.9.

Tests were failing on Travis-CI.

This reverts commit 79d01a8f, reversing
changes made to b838570b.

In log it should not show the empty array.

Programatically define the log level methods and use the Logger constants instead (SyslogLogger didnt define them as I expected)

This reverts commit 29a5aeaa.

When you've got an AR Model and you override the `as_json` method,
you should be able to add default options to the renderer, like this:

    class User < ActiveRecord::Base
      def as_json(options = {})
        super(options.merge(:except => [:password_digest]))
      end
    end

This was not possible before this commit. See the added test case.

Added fix so that file store does not raise an exception when cache dir does not exist yet. This can happen if a delete_matched is called before anything is saved in the cache.

Added ActiveSupport::Inflector.safe_constantize and String#safe_constantize; refactored common constantize tests into ConstantizeTestCases

Updated existing test that fails with this fix (8d63678d).  Before the fix the test was giving a false positive, because file_store.key_file_path would return an empty filename (i.e. test/tmp_cache/4D0/F4D rather than test/tmp_cache/4D0/F4D/xxxx…).

Even though the fix referenced above divides the filename into directories to prevent it from being too long, it seems that 1000 characters will always raise an error, so reducing the key size to 900).

Fixed issue in file store where it could create a filename that was too long for the file system.  (https://github.com/rails/rails/issues/3072)