Minor capitalization tweak to README.
Minor capitalization tweak to README.

wegotpop/pyxero,jarekwg/pyxero,jaymcconnell/pyxero,direvus/pyxero,opendesk/pyxero,schinckel/pyxero,thisismyrobot/pyxero,unomena/pyxero,freakboy3742/pyxero,unomena/pyxeropos