Standardized indentation across .js code

I applied [JSHint](http://jshint.com/) to help standardize indentation. Tab width 4 seemed to be the most common for this project, so I applied it to the rest of the code.

Originally, `jshint .` showed 511 warnings. After standardizing indentation, it now shows 140 warnings.

    $ jshint .
    lib/assert/error.js: line 111, col 17, Bad line breaking before '+'.
    lib/assert/error.js: line 112, col 17, Bad line breaking before '+'.
    lib/assert/error.js: line 113, col 17, Bad line breaking before '+'.
    lib/assert/error.js: line 114, col 17, Bad line breaking before '+'.
    lib/assert/error.js: line 115, col 17, Bad line breaking before '+'.
    lib/assert/error.js: line 116, col 17, Bad line breaking before '+'.

    ...

    lib/assert/utils.js: line 63, col 9, 'ka' used out of scope.
    lib/assert/utils.js: line 63, col 22, 'kb' used out of scope.
    lib/assert/utils.js: line 65, col 5, 'ka' used out of scope.
    lib/assert/utils.js: line 66, col 5, 'kb' used out of scope.
    lib/assert/utils.js: line 67, col 10, 'i' used out of scope.
    lib/assert/utils.js: line 67, col 14, 'ka' used out of scope.
    lib/assert/utils.js: line 67, col 29, 'i' used out of scope.
    lib/assert/utils.js: line 67, col 37, 'i' used out of scope.
    lib/assert/utils.js: line 68, col 13, 'ka' used out of scope.
    lib/assert/utils.js: line 68, col 16, 'i' used out of scope.
    lib/assert/utils.js: line 68, col 22, 'kb' used out of scope.
    lib/assert/utils.js: line 68, col 25, 'i' used out of scope.
    lib/assert/utils.js: line 71, col 10, 'i' used out of scope.
    lib/assert/utils.js: line 71, col 14, 'ka' used out of scope.
    lib/assert/utils.js: line 71, col 29, 'i' used out of scope.
    lib/assert/utils.js: line 71, col 37, 'i' used out of scope.
    lib/assert/utils.js: line 72, col 9, 'key' used out of scope.
    lib/assert/utils.js: line 72, col 15, 'ka' used out of scope.
    lib/assert/utils.js: line 72, col 18, 'i' used out of scope.
    lib/assert/utils.js: line 73, col 34, 'key' used out of scope.
    lib/assert/utils.js: line 73, col 42, 'key' used out of scope.

    ...

    test/vows-test.js: line 184, col 50, Missing '()' invoking a constructor.
    test/vows-test.js: line 197, col 50, Missing '()' invoking a constructor.
    test/vows-test.js: line 314, col 44, Missing '()' invoking a constructor.
    test/vows-test.js: line 387, col 48, Missing '()' invoking a constructor.
    test/vows-test.js: line 433, col 66, Missing semicolon.
    test/vows-test.js: line 450, col 38, Missing '()' invoking a constructor.
    test/vows-test.js: line 475, col 21, Missing semicolon.

    140 errors

I don't know enough about the code base or the team's preferred coding style, so I've left the rest of the warnings alone for now. If you like the `.jshintrc` I've added, I'd be happy to work on this more.