Strip starting and trailing whitespace from environment values

[vandorjw]

Can a flag be added to remove/ignore whitespace from environment values?

In the example below, I denoted spaces with ‧ and a new line with ¶:

• env‧value1‧ -> env‧value1
• ‧env‧value2 -> env‧value2
• env‧val¶ -> env‧val

On a few different projects I've hit a bug where everything looks correct but the difficult to spot whitespace is causes a problem.

I think by default, we would want such a flag to be off, as some uses might legitimately have a trailing space, tab, or line-break in their values.