[IMP-dev] show-changes

I added a little script to IMP tools called show-changes that shows changes in IMP (as announced in the history file) that have occurred since you last updated. The idea is to help people get an idea if there are any changes that would require updating their code before doing svn update so you don't have to spend time updating your code when you are in the middle of something else. And I hope to encourage people to read the change log so they have a sense of what is happening in IMP.

Do ./tools/show-changes from you svn checkout to see what it says. Let me know if there are any problems.