Centerline-width

**New function calls to access centerline types**
- centerlineVoronoi
- centerlineEvenlySpaced
- centerlineSmoothed
- saveCenterlineCSV()

**Clean up cluttered graphs with fewer items**
- Clean up plots on README.md

**Bug fixes: Smoothed centerline accesses evenly spaced centerlines**

- check if invalid polygon due to flipped banks, display suggestions: `Invalid Polygon Due to Flipped Banks, fix recommendation: rerun convertColumnsToCSV() and set flipBankDirection=True (or reset to default 'False' if currently set to flipBankDirection=True)`
- Error handling when left_kml==right_kml
- Bug fixes, remove redundant code and spelling errors

- Update README.md to clarify function calls
- Additional pytests to account for user accidentally uses the same KML file for the left and right banks

Rework functions to work through a riverCenterlineClass object with new argument to interpolate_data to fix jagged edges and gaps that can form in narrow rivers with sparse data

**Convert raw data from Google Earth Pro to CSV**

- extractPointsToTextFile()
- convertColumnsToCSV()

**Find centerline and width of river**

- plotCenterline()
- plotCenterlineWidth()
- riverWidthFromCenterline()
- centerlineLatitudeLongtiude
- centerlineLength
- rightBankLength
- leftBankLength

Beta Release for existing functions:

**Convert raw data from Google Earth Pro to CSV**
- extractPointsToTextFile()
- convertColumnsToCSV()

**Find centerline and width of river**
- centerlineLatitudeLongitude()
- plotCenterline()
- plotCenterlineWidth()
- riverWidthFromCenterline()

Separate functionality into scripts for package functionality

- convertColumnsToCSV()
- plotCenterline()
- centerlineLatitudeLongitude()
- riverWidthFromCenterline()