Fixing Issue #18: automake-1.14 compatibility

autogen.sh currently doesn't recognize automake-1.14 (or any versions of
automake newer than automake-1.13). I've tried to fix this in autogen.sh
by both explicitly adding automake-1.14 and just adding automake to the
long list of `elif`s.
Merge pull request #19 from changlinli/fix-autogen-automake

Fixing Issue #18: automake-1.14 compatibility