add handling of different lengths of scalarTags and correct Usage in ReadMe

[Strandtasche]

Hey,

I've used your script and noticed some things that might be improved.
In one of my examples the scalar "global steps / sec" is slightly shorter than the first column.
in your version the script crashes with an index error, so I added some error handling (substituting the missing values with NaN)

I also noticed some typos in your readme, which I fixed.

Thanks for the script, it helped me a lot

[anderskm]

@Strandtasche Thank you for submitting your pull request. I'm glad you have found the script helpful :-)
Could you provide a minimum working example, which produces different lengths of scalarTags?
That will help me test the code - both now and in the future.

[Strandtasche]

What kind of example do you want? Do you want an tfevents file that has that property or some python/tensorflow code that generates an tfevents file that has different lengths of scalarTags?

[anderskm]

@Strandtasche Some python/tensorflow code is preferable :-)

[Strandtasche]

Sorry for the delay. I didn't manage to produce a minimal working example. I don't even know why my code produces different lengths of scalarTags, maybe I made a mistake somewhere.