Add an .npmignore to greatly reduce the size of the module

[dylang]

You'd think module sizes shouldn't matter on the server, but it adds up when something like bunyan is required by many modules. We hit inode issues caused by the number of files before we hit disk space errors.

I can turn this into a PR if you prefer:

.npmignore

/tmp
/node_modules
*.log
!/test/corpus/*.log
/docs
/examples
/test

[trentm]

Thanks! Will be in bunyan 1.0.1