update maintainers in devscripts
turn on fast_finish on Travis
update HACKING.md re: upgrade verb
recommend `brew cask cleanup` before bug report

A user reported this fixed a problem in #4772.

References: #4857
ensure more informative errors from `dmg.rb`

The logic for better errors was already there; this just makes
sure that another exceptional case is handled, and falls through
to the existing error-check.

References: #4857
don't undent CaskError exception text

The content of `output` is probably not indented, and will be
left-truncated if it is multi-line.  This happens often with
Travis `hdiutil` errors
defensive driving against errors running `hdiutil`

This may not be strictly necessary.  But it should help track
down the `hdiutil` errors, which are persistent, but occasional,
and hard to reproduce. (We pass a flag to `hdiutil` to make
respond in XML.)
Casks/cakebrew: Update to 1.0.7
Merge pull request #4898 from simono/cakebrew-1.0.7

Casks/cakebrew: Update to 1.0.7
Upgrade mumble to v1.2.7
Merge pull request #4899 from kevinoconnor7/update-mumble-1-2-7

Upgrade mumble to v1.2.7
Merge pull request #4892 from rolandwalker/sanity_check_plist_parsing

defensive driving against errors running `hdiutil`
Merge pull request #4888 from rolandwalker/caskerror_exception_format

don't undent CaskError exception text
Merge pull request #4887 from rolandwalker/better_dmg_errors

ensure more informative errors from `dmg.rb`
Merge pull request #4886 from rolandwalker/doc_brew_cask_cleanup

recommend `brew cask cleanup` before bug report
Merge pull request #4884 from rolandwalker/doc_upgrade_progress

update HACKING.md re: upgrade verb
Merge pull request #4882 from rolandwalker/maintainer_update

update maintainers in devscripts
Merge pull request #4883 from rolandwalker/travis_fast_finish

turn on fast_finish on Travis
add more detail to plist parse error messages
fix typo in comments