ticket:62 fix local alignment

ticket:62 fix local alignment
This appears to fix the problem where the local alignment was being
miscomputed. In implementing this I collapsed ExtendedConservedPath into
ConservedPath, and I finished seperating computing the local alignment
from drawing said alignment. Once I seperated the two and could actually
call the core algorithm I was able to add some (simple) unittesting of
the local alignment code, and use some much simpler drawing code.