Use up to date sinon
Preparing for further development

* Run browser tests in `make test`
* Improved `make testwatch`
Older versions of npm do not support carets
Use explicit versions
Allow users to re-register mocha-sinon hooks
Reformat README
Document using mocha-sinon with mocha --watch

Hopefully this will fix #1
Version bump for mocha --watch feature
Merge pull request #2 from elliotf/work-with-mocha-watch

make mocha-sinon work with mocha --watch