Fix convolution spec and outputs in README.md

[BrandonConder]

Closes #35

Updated the conv_spec function in the .py and .ipynb files. Updated README.md to match the changes.

This version of conv_spec was confirmed with the test case inputs against numpy.convolution(a, b, mode='same') and cupy.convolution(a, b, mode='same'). All 3 calculations are in agreement for both test cases.

The spec change doesn't make the problem particularly harder. The solution would require substituting i - j + 1 in place of i + j and adding a check for i - j + 1 > size.

Due to the added check, it may be worth updating the conv_test text from # FILL ME IN (roughly 17 lines) to # FILL ME IN (roughly 18 lines), however it's only a rough number of lines regardless.

[BrandonConder]

Whoops, sorry, this isn't ready yet. I just realized that the "+1" isn't an indexing nuance, it's actually a function of the size of "b" being so small. I'll run some more test cases.

[LIHUA919]

exactly