Bunyan

- [issue 12] Add `bunyan.createLogger(OPTIONS)` form, as is more typical in
node.js APIs. This'll eventually become the preferred form.

- Change `bunyan` CLI default output to color "src" info red. Before the "src"
information was uncolored. The "src" info is the filename, line number and
function name resulting from using `src: true` in `Logger` creation. I.e.,
the `(/Users/trentm/tm/node-bunyan/examples/hi.js:10)` in:

[2012-04-10T22:28:58.237Z] INFO: myapp/39339 on banana.local (/Users/trentm/tm/node-bunyan/examples/hi.js:10): hi

- Tweak `bunyan` CLI default output to still show an "err" field if it doesn't
have a "stack" attribute.

- Fix bad bug in `log.child({...}, true);` where the added child fields **would
be added to the parent's fields**. This bug only existed for the "fast child"
path (that second `true` argument). A side-effect of fixing this is that
the "fast child" path is only 5 times as fast as the regular `log.child`,
instead of 10 times faster.

- [issue 6] Fix bleeding 'type' var to global namespace. (Thanks Mike!)

- Add support to the `bunyan` CLI taking log file path args, `bunyan foo.log`,
in addition to the usual `cat foo.log | bunyan`.
- Improve reliability of the default output formatting of the `bunyan` CLI.
Before it could blow up processing log records missing some expected
fields.

- ANSI coloring output from `bunyan` CLI tool (for the default output mode/style).
Also add the '--color' option to force coloring if the output stream is not
a TTY, e.g. `cat my.log | bunyan --color | less -R`. Use `--no-color` to
disable coloring, e.g. if your terminal doesn't support ANSI codes.
- Add 'level' field to log record before custom fields for that record. This
just means that the raw record JSON will show the 'level' field earlier,
which is a bit nicer for raw reading.