Added a new test for convolve.
"I have added a new Convolve plugin to plugins.py , and I have also a new test for this Convolve plugin."
"I have added Convolve and Normalization plugins, as well as tests for these plugins."
"I have removed the Normalize plugin + test, and I have added a test for Interpolate plugin"
Cleaned up the test_plugins.
Merge pull request #6 from nwwinsor/interpolate_test

Interpolate test and removal of Normalization