Browser detection, settings stored across sessions, ux changes for attribution

[Ethicmeta]

• Added browser detection (extremely basic. if browser object is undefined, it's chrome. otherwise treat it like firefox. this will probably have to change in the future to something like separate build folders entirely, but for now!) and handling storage for each browser.

• added saved options. Change an option, end session, next session has the options populated from prev session.

• relocated attribution block to beginning of code. ex:

// source: http://stackoverflow.com/questions/5113374/javascript-check-if-variable-exists-is-defined-initialized
var setOrNot = typeof variable !== typeof undefined ? true : false;

[Ethicmeta]

@amitness with the vast difference in changes, I removed the use of attribution in the usersettings.html. The functionality still exists in inject.js so all we'll have to do is add the html elements to handle attribution if we want it to. (note, this is only for the copy pasted part and works independently of the url being stored in the history table.)