Merge pull request #38 from peastman/master

Fixed a bug in expression parser
Fixed bugs in handling of random numbers in CustomIntegrator (see bug 1883).
Further cleanup to handling of random numbers by CustomIntegrator
More bug fixes to handling of random numbers by CustomIntegrator
Merge pull request #44 from peastman/gle

Fixed bugs in handling of random numbers in CustomIntegrator (see bug 18...