Updated Proposal to include a pointer back to its context. Updated uses
of proposal to provide that.
optimize: making RDA and AdaGradRDA initialize with values of the tensor they are replacing
Merge pull request #102 from JackSullivan/merge-proposal-context

Updated Proposal to include a pointer back to its context. Updated uses
Merge branch 'master' of https://github.com/factorie/factorie into ParForeach
added execution context