stop_date should be inclusive

[qgeissmann]

metadata <- data.frame(
    file = "Monitor11.txt",
    start_datetime = "2017-07-01 09:00:00",
    stop_datetime = "2017-07-01",
    region_id = 1)

should read all data, on 2017-07-01, after 09:00:00. Instead, we get:

Error in find_dam2_first_last_lines(path, start_datetime, stop_datetime,  : 
  start_datetime is greater than stop_datetime. Cannot fetch any data!

To reproduce, extract this file: Monitor11.zip

Thanks, @hanhanhankim for reporting the issue