Sec-edgar-downloader

- Added the ability to specify the number of filings to download
- For example, you can download the latest 10-K for MSFT with this command: `downloader.get_10k_filing_for_ticker("MSFT", 1)`
- This is available for all non-bulk methods: `get_8k_filing_for_ticker`, `get_10k_filing_for_ticker`, `get_10q_filing_for_ticker`, `get_13f_filing_for_ticker`, `get_sc_13g_filing_for_ticker`, `get_sd_filing_for_ticker`, and the CIK equivalents

- Internal renaming changes

- Reduced size of ticker validation data by changing an internal data structure

- Fixed the "FileNotFoundError" on import

- Tweaked PyPI description

- Filing downloads are now handled in chunks to improve download and save speed
- Removed get_select_filings_for_ticker() to reduce redundancy
- Added support for SC 13G filings
- Separated ticker and CIK class methods for easier use
- Added ticker symbol validation