Now successfully completes VPATH build via `make distcheck'
Another try
removing AM_SILENT_RULES([yes]) from configure.ac temporarily
call ls
Now there is a target for webvtt-config.h in libwebvtt and libwebvttxx as well, which solves the VPATH and SRCDIR builds on my unix VM. perhaps Travis will survive
Merge pull request #107 from caitp/build-system

Build system updated to fix VPATH builds (eg distcheck) as well as SRCDIR builds (eg travis)