CLN/DOC: Change instances of "Pandas" to "pandas" in documentation
I noticed what seemed to be inconsistencies in capitalization, and this PR "fixes" what I noticed. Instances in old release notes not touched, likewise for titles of talks.

If this is incorrect or unwanted, please feel free to close.
 @jorisvandenbossche  ?
 @jreback Do you know if there was ever a discussion on the preferred spelling/capitalization? It seems that the website (http://pandas.pydata.org/) consistently uses lower case.

But the website seems to also consistently put it in italics. Would that also be preferred for the docs?

My question was also if it is also needed to keep it lower case if it is the first word of a sentence, but it seems this is how it is done in most places.
 pretty sure it should be lowercase

italics I think are just for emphasis / to break it up

so I am indifferent to italics , +1 for pandas
 +1. and IMO no need for italics here.
 I just find that sentences that start with a word without capital look a bit awkward, and then using italic can stress that it is not a normal word but a proper name. But OK to do this only on the landing page (as the website)
 @bwignall Can you rebase this?
 Rebased.

Agreed that it feels awkward to start a sentence without a capital letter. My reasoning was, if "pandas" is the proper noun, that capitalization should be used everywhere, including the beginning of a sentence. Of course, happy to revert those if that is incorrect.
 OK, but for now the rule is then 'always and everywhere lowercase". So this is OK, merging. Thanks!
