added IQL wrapper for delete
influx_connection gains new argument curl_options to control http communication (#36)
influx_write function gets measurement_col argument to enable writing a data.frame with multiple measurements with only one function call
package dependencies specified for dplyr and purrr (#21, #38, #39)
new internal helper functions for httr::GET and httr::POST
influx_write function argument xts changes to x (method is now generic)influx_write now accepts data.frames to upload mulitple tags and fields per timestamp (#20).correct parsing of json structure without statement_id (#32).
special characters in xts attributes are now supported (#30).
Fix special character representation in show_series.
Using double quotes in string arguments of influx_query wrappers (e.g. influx_select, show_tag_values) (#22).
IQL wrapper functions with no expected return value now use influx_post instead of influx_query.
Fix coercion error in influx_write() in case of sub-second accuracy (#25).
influx_select() correctly parses integer arguments (#27).
Significantly improved performance of influx_query() (#28).