Added Mramba 2017 mid-upper arm circumference calculator

Summarized from the abstract: mid-upper-arm circumference (MUAC)-for-age z score for 5-19 year olds that accord with the World Health Organization growth standards. Curves were created using the Health Examination Survey (HES) / National Health and Nutrition Examination Survey (NHANES) US population datasets (age 5-25 years), which were used to construct the 2007 WHO growth reference for body mass index in this age group, and were merged with an imputed dataset matching the distribution of the WHO 2006 growth standards age 2-6 years.