Fix toasts appearing under modal

[Blackbaud-JackMcElhinney]

Added z-indexes to toaster and toast so they appear over the modal background and can be closed while the modal is open.

Resolves: #1708

[blackbaud-sky-savage]

Tests passed. Automated cross-browser testing via BrowserStack and Travis CI shows that the JavaScript changes in this pull request are: CONFIRMED

Commit: 9e7f8e9
Build details: https://travis-ci.org/blackbaud-sky-savage/skyux2/builds/396472348

(Please note that this is a fully automated comment.)

[codecov-io]

Codecov Report

Merging #1756 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1756   +/-   ##
=======================================
  Coverage   99.98%   99.98%           
=======================================
  Files         410      410           
  Lines        8585     8585           
  Branches     1267     1267           
=======================================
  Hits         8584     8584           
  Misses          1        1

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[Blackbaud-SteveBrush]

Since we're setting the z-index of the parent "toaster" component, this is redundant.

[blackbaud-sky-savage]

Tests failed. Automated cross-browser testing via BrowserStack and Travis CI shows that the JavaScript changes in this pull request are: BUSTED

Commit: c378941
Build details: https://travis-ci.org/blackbaud-sky-savage/skyux2/builds/399712301

(Please note that this is a fully automated comment.)

[blackbaud-sky-savage]

Tests failed. Automated cross-browser testing via BrowserStack and Travis CI shows that the JavaScript changes in this pull request are: BUSTED

Commit: df9b9b8
Build details: https://travis-ci.org/blackbaud-sky-savage/skyux2/builds/404916729

(Please note that this is a fully automated comment.)

[blackbaud-sky-savage]

Tests passed. Automated cross-browser testing via BrowserStack and Travis CI shows that the JavaScript changes in this pull request are: CONFIRMED

Commit: c15f7b9
Build details: https://travis-ci.org/blackbaud-sky-savage/skyux2/builds/405039003

(Please note that this is a fully automated comment.)

[blackbaud-sky-savage]

Tests failed. Automated cross-browser testing via BrowserStack and Travis CI shows that the JavaScript changes in this pull request are: BUSTED

Commit: c6ee354
Build details: https://travis-ci.org/blackbaud-sky-savage/skyux2/builds/405064621

(Please note that this is a fully automated comment.)

[blackbaud-sky-savage]

Tests passed. Automated cross-browser testing via BrowserStack and Travis CI shows that the JavaScript changes in this pull request are: CONFIRMED

Commit: 61433f0
Build details: https://travis-ci.org/blackbaud-sky-savage/skyux2/builds/405095118

(Please note that this is a fully automated comment.)