Fixes bug #113: Run keepalive setInterval outside NgZone

[michaelmills]

This is a fix for issue #113 to allow Protractor to continue without waiting for synchronization with Angular.

issue #113

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines: https://github.com/HackedByChinese/ng2-idle/blob/master/CONTRIBUTING.md#pr
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here) https://github.com/HackedByChinese/ng2-idle/issues/113

What is the new behavior?

Does this PR introduce a breaking change? (check one with "x")

[ ] Yes
[x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[coveralls]

Coverage increased (+0.003%) to 99.372% when pulling 04e3d4c941cffbae8190c6833c73718507cbd70a on michaelmills:bugfix/issue-113 into 11f2796a580f416943aec9f18f9607c403c7ce2e on HackedByChinese:master.