fixes #34

Otherwise Travis would accept PRs that ignore our linting rules

* feat: ignore attributes and strip tag prefixes during xml parse
* fix: getAllEvents() for iCloud calendars
* test: add fixtures for iCloud calendar style responses
* docs: add 401 error hint to README.md

feat: implement native promises

BREAKING CHANGE: update Node version to v8.0.0

Fixes #23

Switch to standard version

Fix: Convert dates to ISO-Strings

Return all dates (`start`, `end`, and `createdAt`) as ISO-Strings,
instead of Date objects to maintain consistency.

BREAKING CHANGE:

The dates were returned as a mix of ISO-Strings and Date Objects
in previous versions.

To migrate your project, confirm that you are handling the dates
received from scrapegoat correctly.

WIP: Handle timeout

Solve Filter events bug

Filter events