Fixes P/E Ratio to return the correct value

Before this fix :pe_ratio doesn't return the correct value.
`YahooFinance.quotes(["GOOG"],[:pe_ratio]) #=> [#<OpenStruct symbol="GOOG", pe_ratio="6.40">]`

It should be 25.07, and with this fix it is.  I cross referenced this site, http://msexcelvancouver.com/blog/how-to-call-the-free-yahoo-finance-api-to-get-stock-data-excel-vba/, to make sure the other symbols were correct, and everything else seemed right.

 I also removed some two minor errors from the read me.