vscode 1.11.x doesnt seem to properly remove editors from active array

[ryanluker]

reproduce:

• add coverage to editors
• close editors or navigate away
• regenerate the lcov file
• see warning messages in debug log about editor having been disposed
• no user facing issues other then editor array not being cleaned up

code:

Seems to be a change in the disposal pattern for the editors in the 1.11.x release, when debugging the problem it seems as if the wrong conditional flow is happening for the editors that have been disposed. https://github.com/ryanluker/vscode-coverage-gutters/blob/master/src/gutters.ts#L61

work:

• Find adaptable work around or increment min version to 1.11.x
• (optional) Add metric to capture vscode version