tf2outpost price integration

Grabs prices of items from backpack.tf and adds them to tf2outpost.comVersion 1.4.1
Fixed bugs with some non-Australium items display Australium prices
Fixed bug where various items would incorrectly display "???"
Fixed bug where some items with paint would display mix text

Version 1.4.0
Added ability to toggle buds as currency.
Removed unused "advanced settings" button.
Fixed bug where item prices were being cached even after a price update.

Version 1.3.3
Fixed bug where users had to manually refresh prices after first installing.

Version 1.3.2
Rewrote the extension from scratch.
Added page action menu that allows users to turn off features.
Removed infinite scrolling until a better implementation is complete.
Added ability to manually refresh prices.
Fixed various bugs.

Version 1.2.3
Added support for more pages and fixed bug with never-ending-tf2outpost where label never updated.

Version 1.2.2
Fixed caching bug that caused prices to not load

Version 1.2
Rewrote code base to be more manageable and extendable.
Fixed bug with never-ending-tf2outpost when searching.

Version 1.1.6:
Paint is now factored into the price of painted items.
Added a feature to load the next page when the bottom of the current page is reached.

Version 1.1.4:
Fixed bug with cross-origin request permissions.