Merge branch 'master' of https://bitbucket.org/fenics-project/dolfin
Revert "fix issue #4" - this commit should not go here

This reverts commit 9922f0cf440e6bf6dc21ddb9ada0d4a096ebe535.
fix in incremental SystemAssembler
add unit test and docstring for incremental SystemAssembler
Merged in blechta/dolfin/blechta/SystemAssembler (pull request #9)

fix bug in incremental SystemAssembler