Update calls to getPsnForPid to just in time

There's no need to call this before we actually need it - this resolves an issue where the call fails for certain apps and needlessly blocks the global variant of these methods.

Closes issue 48
Merge pull request #49 from jtatum/global

Update calls to getPsnForPid to just in time
Merge pull request #46 from ldtp/master

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Merge pull request #3 from pyatom/master

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