Revised coverity_scan addon

Using an externally fetched script to handle the Coverity Scan build
to increase the stability of the addon.
fix(objective-c): don't open the simulator when running specs

Close travis-ci/travis-ci#1872.
Use env TRAVIS_BYPASS to override default stage
Make bypass function more innocuous
Correctly set Script#enable_bypass_main_stage
Remove main stage bypass
Merge pull request #195 from aceofspades/coverity_scan

Revised coverity_scan addon
Minor fixes to coverity_scan addon
refactor(deploy): don't share instance variables across deployments
Merge pull request #196 from aceofspades/coverity_scan

Minor fixes to coverity_scan addon
Coverity addon ENV updates
Merge pull request #198 from aceofspades/coverity_scan

Coverity addon ENV updates
if the node version is a float, convert it to a string
remove the commit message for the time being
utf-8 chars seem to interfere with the build script execution, causing builds to hang
https://github.com/travis-ci/travis-ci/issues/1915
Merge pull request #197 from travis-ci/hh-refactor-multiprovider-deploy

refactor(deploy): don't share instance variables across deployments
Fix specs that got left behind

7851a7f forgot to revert the specs
Namespace remaining Coverity Scan env vars
Merge pull request #200 from aceofspades/coverity_scan

Namespace remaining Coverity Scan env vars