This function generates a time stamp of the format 'yymmdd_hhmmss'.
This is a support function and is not intended for direct use.
tstamp()String containing the timestamp in the format 'yymmdd_hhmmss'.
Other Support: 
camel_clean(),
check_inputs(),
combine_signals(),
cut_hour(),
extract_date_range(),
extract_hr(),
heat_colours(),
is_date_format(),
maxmin(),
p_test(),
pairwise_count(),
plot_WOE(),
read_preamble(),
rgb2hex(),
totals_bind(),
totals_col(),
totals_reorder(),
us_to_space(),
wrap()