Custom separators and more

— now you can set own BEM separators (by default '__' and '_' ). See bem section at config.json;
— bugfix. Added more tests;
— new template placeholder {{cursor}} (see more at readme);
— new key -o and relevant config section editor-open-command (see more at readme);
— added english description;
— shortcut for bemy. So now call bemy with just bemy command. Don't forget install with -g.