Added "stroustrup" option for brace-style

The `brace-style` rule now takes one option, which can be either
"1tbs" or "stroustrup". The only difference between the two is that
"stroustrup" requires `else`, `catch`, and `finally` to be on a new
line after the closing curly brace:

    // 1tbs

    if (foo) {

    } else {

    }

    // stroustrup

    if (foo) {

    }
    else {

    }

In addition, I've set the `.eslintrc` for ESLint to explicitly use the
"1tbs" option.

Fixes #645
Fixes #644
Merge pull request #646 from iancmyers/brace-style

Update: Added "stroustrup" option for brace-style (fixes #645 and fixes #644)