Use a temporary directory for preprocessor output

[jlewi]

It looks like when I use fairing to convert my notebook it outputs a ".py" file in my current directory.

Would it be better to output it into a temporary directory?

If it outputs it to my current directory then it would tend to get checked into source control which may not be desirable.

[karthikv2k]

Would it be better to output it into a temporary directory?

Yes that would be better.

Related issue: #75

[jtfogarty]

/area engprod /priority p2