Add minimum attribute requirement in gems.json

[karakasis]

https://github.com/brather1ng/RePoE/tree/master/data

Use this open source information , examine each gem in gems.json and find attr required .
Maybe save them in "attributes" : {
"dex" : 0,
"int" : 0,
"str" : 0
}

Then change the code needed to read values, and make a new value in Gem class to keep them in some sort of inner class.