Add Support for IE

[jasonleibowitz]

What does this PR do?

• Adds support for older IE browsers.
• Fixes an issue where the Outlook ics download wouldn't work properly.
• If description, location, or title aren't provided as part of the event don't display undefined.

[codecov-io]

Codecov Report

Merging #14 into master will not change coverage. The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #14   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           4      2    -2     
  Lines          66     18   -48     
=====================================
- Hits           66     18   -48

Impacted Files	Coverage Δ
src/lib/utils.js	100% <100%> (ø)	:arrow_up:
lib/enums.js

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 76a4e66...663ef83. Read the comment docs.

[coveralls]

Pull Request Test Coverage Report for Build 38

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-18.8%) to 77.273%

---

Totals
Change from base Build 33:	-18.8%
Covered Lines:	18
Relevant Lines:	18

---

💛 - Coveralls