Add an ext_path configuration option to load external custom code.

This provides an extension point to load in customized Razor models,
kickstart templates, additional persistence backends, etc.

The `ext_path` directory defaults to a path beside the directory
containing Razor's lib/ directory. For example, if Razor is installed
into `/opt/razor`, the `ext_path` directory defaults to
`/opt/razor_ext`.

The extension mechanism will look for an `ext.rb` file in the root of
the `ext_path` directory and require it if it exists. It is up to
extension authors to add further require statements and initialization
logic in this file. Note that the `ext_path` will be added to Razor's
Ruby LOAD_PATH, so a file in the `ext_path` directory called
`acorp/model/acorp_centos_6.rb` can be required in `ext.rb` with:

    require 'acorp/model/acorp_centos_6'
Fixed size undefined error in tail method extension of class File.
Merge pull request #484 from mhanco/bug/master/slice-log-class-file-tail-method-size-undefined

Fixed size undefined error in tail method extension of class File.
(packaging) Use the packaging loader for tasks

The packaging repo now uses an explicit loader which handles loading the
various rake tasks in packaging. This commit updates the Razor Rakefile to
use the loader instead of a glob of the ext/packaging/tasks directory. We move
this load into the rescue LoadError block because the packaging repo won't
always be there, but if it is, we want to load it.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
(packaging) Remove Ubuntu Oneiric from build targets

Oneiric is EOL, and we are no longer building for it. This commit removes the
Oneiric target from the build list for Razor.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Merge pull request #491 from MosesMendoza/packaging/master/remove_oneiric

(packaging) Remove Ubuntu Oneiric from build targets
Merge pull request #492 from MosesMendoza/packaging/master/update_packaging_loader

(packaging) Use the packaging loader for tasks
Merge branch 'ext-path' of https://github.com/blueboxgroup/Razor
Import "The road forward for Razor" as the primary readme

This brings information about what is going on with Razor into the forefront
of visibility.  Old information is still preserved in a separate file.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Merge branch 'master' of https://github.com/puppetlabs/Razor
adding some windows support