tools(changelog): handle non merge commits

Merge pull request ampproject#2772 from jessedijkstra/patch-1

Change the spelling of "availbale" to "available"

Merge pull request ampproject#2688 from powdercloud/amp-accordion-doc…

…umentation-update

Update the amp-accordion documentation

Ensure that all extensions are processed

Merge pull request ampproject#2625 from erwinmombay/fix-cyc-changelog

fix changelog to handle PR's that have a merge coming from master

Merge pull request ampproject#2566 from dvoytenko/access56

Ensure that pingback is executed when directly requested

Merge pull request ampproject#2502 from omegdadi/issue2491

Updated amp-fill-content to workaround IOS

Merge pull request ampproject#2429 from erwinmombay/fix-bug

remove reference to whenFirstLayoutCompleteResolve_

whitelist branches with the name amp-release-.* for a travis build

Merge pull request ampproject#2341 from cramforce/unique-canary

Turn on unique origins for dev channel by default.