Feature/time aware transit networks

[sablanchard]

Merge PR https://github.com/UDST/urbanaccess/pull/86 first before this one.

New feature: Adds the optional ability to include arrival and departure times in the generated network. Adds the optional ability to pad the end time range when subsetting a transit network in order to extend your active transit network beyond the specified operational time range. Changed the selection of transit network stops and trips from > and < time range to >= and <= time range in order to explicitly include stop times that also equal the min and max time range - Note: this change will produce slightly larger transit networks than prior versions. Big thanks to @bouzaghrane for his initial PR #83 that started the features in this PR and his input on implementation and use cases. Simple use case demo notebook that illustrates this new functionality will be added in a future update.

Begins to address feature request described in: https://github.com/UDST/urbanaccess/issues/78 and https://github.com/UDST/urbanaccess/issues/51

Details on changes:

• Updated create_transit_net() with new parameters:
  • timerange_pad: number of hours, minutes, seconds to pad after the end of the time interval specified in 'timerange'
  • time_aware: boolean to indicate whether the transit network should include time information. If True, 'arrival_time' and 'departure_time' columns from the stop_times table will be included in the transit edge table where 'departure_time' is the departure time at node_id_from stop and 'arrival_time' is the arrival time at node_id_to stop
• Changed stop time selector > to >= and < to <=
• Removed py27 and 35 from travis for future UrbanAccess end support of py27 and 35

[bouzaghrane]

This is great! Thanks @sablanchard

[sablanchard]

@smmaurer removed py27 and 35 from travis via: https://github.com/UDST/urbanaccess/pull/87/commits/35a0d0b3ecdd9bde1ed679dc90e7dd603a08795d