Simple Product validations

Presence was an issue so I validated for presence. The main problem
that this commit solves is the numericality validation of the price
attribute. I check for the value to be 'greater than or equal to'
0.01 and not 0 because 0.01 is more strict.

If a user entered 0.001 as a price, active record would round to
two decimal places and the value would get validated/added to the
persistence layer.
image_url validations

Validates the format of the value passed into the image_url field
of the form. The file must end with a valid image extension.
Validates uniqueness of a products title as well.
Product create and update tests

Creates valid Product setup data for use in HTTP Post and Patch requests
make image_url validation case insensitive
test our model validations and create a new fixture for the model
Merge branch 'master' of https://github.com/arcin/depot
generate Store Controller with index action
set the root of the site to store index page
show all products at store index page. style index page. retrieve products in order
add banner to layout
integrate sass for application stylesheet
application styles
fix typo in ruby fixture
test store index page dom structure
temporarily enable caching in development mode
latest scope

Creates a scope that returns the most recent product. Also includes a
model test.
Add caching to store Index Page

Cache the store index page, tying the Store cache to the latest Product model,
and Entry cache to each individual product in the store.

Turn off caching in development because the caching has been confirmed to be
working.
Merge pull request #2 from arcin/store

Store