Sort plugins so people can have "load orders".

This allows for people to do something like "_plugins/1-autoload-global.rb" and have it load first and so on making it much easier to organize code and have a "header file" that does all the requiring up front if it's needed for all plugins.
Parse TOML or YAML in Jekyll::Configuration.
Better config file parser error if it's not there.
Give that LoadError a good message.
require the TOML gem, idiot.
Add some unit tests for TOML integration.
Fix favicon’s type
Merge pull request #1772 from penibelst/no-x-icon

Fix favicon’s type
Update history to reflect merge of #1772
Merge pull request #1765 from mojombo/tomlify

Add support for TOML config files
Update history to reflect merge of #1765
Merge pull request #1682 from envygeeks/patch-1

Sort plugins so people can have "load orders".
Update history to reflect merge of #1682