Lowercase spelling of mpld3 on docs frontpage

Most of our docs already use lowercase spelling.
Moreover this is more consistent with the logo,
which also uses lowercase letters.
Merge pull request #167 from dloss/lowercase-mpld3

Lowercase spelling of mpld3 on docs frontpage
Use CamelCase spelling for JavaScript in docs

The official spelling is JavaScript, with a capital J
and a capital S.
See https://developer.mozilla.org/en-US/docs/Web/JavaScript

Only change the documentation for now, in order not to break
any code.