Update corrplot.R: option to remove leading 0s added

[erinnacland]

I added an option to remove the leading zeros for the correlation values in 'method = "number"' and 'addCoef.col'. It is by default turned off.

[erinnacland]

(this option has also been requested in issues):

#267

[jeffzemla]

This PR has a few issues:

1. It does not load. There is a duplicated if statement that causes an error (lines 890-891 should be deleted)

2. del.lead.zero=TRUE overrides number.digits setting (i.e., it forces number.digits=2)

I suggest replacing line 328 with:

del.lead.zero = function(val) {sub("^(-?)0.", "\1.", val) }}

and reverse the order of the format/del.lead.zero functions when called later so it executes on the format()ed string:

change line 713 to:

labels = del.lead.zero(format(round(x, number.digits), nsmall = number.digits)),

change line 896 to (and fix the parens so nsmall=number.digits is passed to format()):

labels = del.lead.zero(format(

Not sure how (or if possible) to edit a PR, but if @taiyun would like I can submit a new PR with the changes, add an example to the vignette, add to ?corrplot, and add a MRE to #274