Daily data should be normalized to midnight

[PoorRican]

For daily candle data, timestamps should be normalized to midnight so that they may be properly indexed by Timestamp. This allows indexing to return a Series instead of a DataFrame. This would reduce boilerplate code for getting primitive values from indexing and reduce unnecessary functions (eg: BBANDSRow._extract_rate().

This would close #83

While daily data should be derived from resampling (as per #73), daily candle data should be used for resampling larger frequencies such as weekly or monthly data.