Remove the transient cache

These transient caching lines aren't present in the other widgets and cause a problem when people are using WPML. The problem is when switching between language this widget stays in the base language. Removing the transient cache lines resolves the problem. I suggest having them permanently removed as they don't seem to effect anything with this widget.
Remove get_permalink from redirect

I removed get_permalink and it appears that jigoshop_get_page_id('cart') is already returning the permalink to the cart. When it was combined together it was returning nothing and exiting the page execution. This was on an install using the post title permalink structure.
Merge pull request #830 from mcfarljw/dev

Remove the transient cache and fix checkout redirect
update for 1.6.4