Lakshmi

Fixed
- Fixed crash when a portfolio consists of only ManualAssets.

Changed
- `lak list performance` and `lak info performance` commands will print
the performance stats till today as opposed to the last saved checkpoint.
- Deleted unnecessary lakshmi.analyze.Analyzer interface.
- Rename lakshmi.Portfolio.assets to lakshmi.Portfolio.list_assets for
consistency.
Fixed
- Vanguard's website SSL certificate was throwing errors. Disable SSL checks
until I figure out a better solution.

Fixed
- AttributeError when ibond interest rates are fetched.
- Add dependency to latest version of yfinance (removes some warnings that
older version is throwing).
- Renamed lakshmi.Portfolio.assets to lakshmi.Portfolio.list_assets for
consistency.

Fixed
- yfinance threw error while fetching names of tickers from yahoo finance.
The latest version fixes that -- lakshmi now explicitly depends on the latest
version.

Fixed
- Connection issues with the Vanguard website.

Changed
- If for some reason interest rate data is outdated (e.g. if user doesn't
update ibonds module), IBonds class will no longer abort when printing
interest rates for IBonds. Instead it will just output empty interest rates.
IBonds value method will still abort if the missing interest rate are needed
to calculate the current value of IBonds.
- `lak edit` commands now accept comma-separated floats (e.g. when entering
shares or dollar values). This makes it easy to paste values from websites.

Fixed
- lakshmi was stuck pulling prices for I/EE bonds. Treasury Direct seems to be
blocking http. Use https instead of http for EE bonds (also see below).

Changed
- For fetching I Bonds, lakshmi now uses the `ibonds` package instead of
Treasury Direct website. The I Bond values are calculated locally instead of
fetching them from internet, making updating the prices of I Bonds much
faster. Also, we now return the fixed rate in addition to the composite rate
when fetching information about I Bonds (e.g. when using `lak info asset`
command or `lakshmi.assets.IBonds.list_bonds()` method).