(#2435) - disable saucelabs for now

*in the distance, the sound of a bugler mournfully
playing Taps can be heard*
(https://github.com/pouchdb/pouchdb/issues/445) Implement Incremental MD5 calculation

Replace jkmyers-md5 with Spark-MD5 in order to calculate MD5 hashes
incrementally. The use-case for this change is to avoid blocking the UI
thread when adding large attachments.
(#445) Use setImmediate and code style changes.
fix test
rm unused variable
coerce to buffer
or just don't use a buffer
Merge branch 'explorigin-445' of github.com:calvinmetcalf/pouchdb into calvinmetcalf-explorigin-445

Conflicts:
	lib/utils.js
Merge branch 'calvinmetcalf-explorigin-445' into 445