use getProperty instead of getenv else it yields nil and throws

CompilerException java.lang.IllegalArgumentException: No implementation
of method: :open of protocol:
#'clojurewerkz.titanium.graph/TitaniumGraph found for class: nil,
compiling:(graphs1.clj:10:8) 

though, getenv with "tmp" or "temp" would've worked too
Merge remote-tracking branch 'upstream/master' into somepatch1
Merge pull request #2 from AtKaaZ/somepatch1

fix exception when trying berkeleydb example