Source 1: http://www.techtimes.com/articles/93481/20151013/how-to-install-android-6-0-marshmallow-on-your-nexus-4.htm
Source 2: http://dmitry.gr/index.php?r=06.%20Thoughts&proj=02.%20Android%20M%20on%20Nexus4
Source 3: https://plus.google.com/+AldrinHolmes20/posts
Google did not release Marshmallow for Nexus 4 (only Nexus 5,6,7 and 9). So Dmitry Grinberg released his Marshmallow Nexus 4 build last week. Yesterday, Aldrin Holmes released his own build as well. Based on some reading, the latter seems to have less problems. Nonetheless, both builds work.
Here's Dmitry's ROM
Here's Aldrin's ROM
I did not tamper with either of the files. You can verify from sources 2 and 3. The tutorial on how to install is in source 1 but I'm pretty sure most of you here know your way around Android. I hope this helps.