Handle fileSize limit event with option

Handle 'limit' event when file is over fileSize

Added md5 checksum for each file upload

Fixes #50. Default function argument value is not supported in Node 4 and 5. Although this package no longer supports Node 4 or 5, this seems like a harmless update.

Updating devDependencies. Updated to latest version of Google eslint rules. Updated test/server.js to be lint-happy.'

Add error handlers for parser errors

Feature - Allow extension preservation with safe file names

Refactor server.js to allow for different options to be provided during testing

Bumped the version number to 0.1.3

Misc reformatting.

Fix readme

improve performance for large files

Using `buf = Buffer.concat([buf, data]);` on the data event copies the
data in a new larger buffer everytime. Instead, store the intermediate
small buffers in an array and concat only at the end.