stackr: new functions

v.0.2.7 Added a NEWS.md file to track changes to the package. New function: individuals2strata. Several functions in stackr and assigner requires a strata argument, i.e. a data frame with the individuals and associated groupings. You can do it manually, however, if your individuals have a consistent naming scheme (e.g. SPECIES-POPULATION-MATURITY-YEAR-ID = CHI-QUE-ADU-2014-020), use this function to rapidly create a strata file. New function: tidy_genomic_data. Transform common genomic dataset format in a tidy data frame. Used internally in stackr and assigner and might be of interest for users. New function: read_long_tidy_wide. Read genomic data frames in long/tidy and wide format. Used internally in stackr and assigner and might be of interest for users. New function: stackr_imputations_module. Map-independent imputation of missing genotype using Random Forest or the most frequent category. Impute genotypes or alleles. Used internally in stackr and assigner and might be of interest for users. New function: find_duplicate_id Compute pairwise genome similarity to highligh potential duplicate individuals