Make map viewport resize for interactive maps

[Josh-ES]

There was previously a conditional in place where only non-interactive maps would resize their viewport when the window was resized. This was because static maps would not be centred correctly if the viewport was not resized. However, interactive maps were not introducing new map tiles when the window was resized, resulting in situations where the window is expanded, leaving blank tiles around the map.

This pull request adds an onAllLoad method to the cache code, which fires a passed callback when all scripts in the script map are loaded. It also fixes a deprecated use of gulp-typescript in the gulp file. Finally, it ensures that all maps have their viewports resized on window resize events.

Closes #8

[coveralls]

Coverage decreased (-2.4%) to 94.85% when pulling 9010d16 on feature/resize into c364b8d on master.

[coveralls]

Coverage increased (+0.2%) to 97.479% when pulling 58c012c on feature/resize into c364b8d on master.