If the tempDir is not writable, try the system's global cache dir
bug #53 If the tempDir is not writable, try the system's global cache dir (javiereguiluz)

This PR was squashed before being merged into the 1.0-dev branch (closes #53).

Discussion
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If the tempDir is not writable, try the system's global cache dir

This fixes #51

Commits
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c4f5889 If the tempDir is not writable, try the system's global cache dir