Merge pull request #274 from VinithSamson11/dev

The smileih5.py file was tested with latest SmileiPIC (v5.0) & Happi version. The test data were dumped from Smilei version v5.0 and the the output values are compared with latest corresponding version of Happi. The relative error of the mode expansion was in the order of 10^-15 comparing happi's output with postpic's output from this commit.