XAVIER 3.1.1

• New contributing guide available on GitHub and the documentation website. (#114, @kelly-sovacool)
• New xavier debug subcommand to determine the base directory for debugging purposes. (#114, @kelly-sovacool)
• Upgraded ccbr_wes_base docker to v1.1.0 with updated GATK version to v4.6.0.0 (#116, @samarth8392)
• Upgrade multiqc container to use v1.15. (#117, @kelly-sovacool)
• Upgrade memory for rule "bwa_mem" to 100G (#118, @samarth8392)