Change default quantiles from IQR to 95% CI in augment_linelist()

[CyGei]

augment_linelist() uses q25/q75 (IQR) as default quantiles for the summary_fns argument.
Propose changing to q025/q975 (95% credible interval) which is more standard.

Current:

q25 = function(x) quantile(x, .25, na.rm = TRUE),
q75 = function(x) quantile(x, .75, na.rm = TRUE)

Proposed:

rq025 = function(x) quantile(x, 0.025, na.rm = TRUE),
q975 = function(x) quantile(x, 0.975, na.rm = TRUE)

Lines to change: 43-46