Another fix for start and end date.

Fix for start date end date issue

FIxed startdate enddate order in calling summaries

No idea how nobody noticed this bug.

Merge pull request #7 from rdeanar/master

FIxed heartbeats "Missing date" error. Added implementation of "durations" method.

Dropped support for php versions lower than 5.6

Added new resource for heartbeats. Optimized code and upgraded guzzle.

Merge pull request #4 from stemsmit/patch-1

URI change for dailySummary to match Wakatime API

Merge pull request #3 from chrisvogt/add/api_stats_resource

Connects the WakaTime stats() resource

Changed url endpoint.

Allow for chaining after setApiKey.