Remove misplaced typename.
Provide non-const version of SerialExecutor::execute for MSVC.

This is related to the bug http://connect.microsoft.com/VisualStudio/feedback/details/773565/cannot-call-const-forwarding-call-wrapper-result-of-std-bind#
Merge pull request #210 from endJunction/CorrectMSVCCompilerErrors

Correct MSVC compiler errors