fix(infinite-loop): Rebased commit gets a different sha1

[samber]

When a commit is rebased, git create a new sha1, but github keep a reference to the old one (see GET /repos/:owner/:repo/commits).

When starting github-changelog by using a rebased commit as limit, the module enter in an infinite loop, because it keeps calling the pageOfCommits function until it find the limiting sha1 (the old one, not existing anymore in the commits list).

This fix is just a work around and does not really solve this issue. Github is smart enough to stop returning commits when the limiting sha1 or his alias is reached.