CLN: Update pr merge script
CLN: Update pr merge script

Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1744 from cpcloud/improve-merge-pr and squashes the following commits:

7ae29a6 [Phillip Cloud] Try passing the json parameter
ba959f2 [Phillip Cloud] Escape strings
c896b69 [Phillip Cloud] Not v3
ce5206a [Phillip Cloud] Try with v3
31e77de [Phillip Cloud] Remove comment
b9ccc33 [Phillip Cloud] Try with header
2484f90 [Phillip Cloud] Basic auth
6a84ef8 [Phillip Cloud] Add username and password
40cdb7e [Phillip Cloud] Access token param
2a775cd [Phillip Cloud] Add oauth token
29dc439 [Phillip Cloud] Enable merging
fadba1d [Phillip Cloud] Use GitHub API rather than local git hacks
52d9828 [Phillip Cloud] CLN: Clean up dev/merge-pr.py
ibis-project/ibis,cpcloud/ibis,cloudera/ibis,cpcloud/ibis,ibis-project/ibis,cpcloud/ibis,cloudera/ibis,ibis-project/ibis,cloudera/ibis,ibis-project/ibis,cpcloud/ibis