Centerline-width

New Coordinate Option: "Relative Distance" vs "Decimal Degrees"
**New optional argument to designate which coordinate system to use: `coordinate_type`**

`Decimal Degrees`: Default option that uses a latitude/longitude of each point

`Relative Distance`: New option that converts each point to a distance from the first point on the left bank

Function that accept new coordinate_type option:
- plotCenterline()
- plotCenterlineWidth()
- saveCenterlineCSV()
- saveCenterlineMAT()

New river class options:
- centerlineVoronoiRelative
- centerlineEqualDistanceRelative
- centerlineEvenlySpacedRelative
- centerlineSmoothedRelative
- left_bank_relative_coordinates
- right_bank_relative_coordinates
- bank_polygon_relative
- top_bank_relative
- bottom_bank_relative
- starting_node_relative
- ending_node_relative
- bank_voronoi_relative
- x_voronoi_ridge_point_relative
- y_voronoi_ridge_point_relative

_Bug fixes and README.md edits_

_Pytests: 205 tests_

README.md edits and ZOrder for Centerline

**Update README**
- Instructions to Generate KML files from Google Earth Pro
- Details about the purpose and example images for `equal_distance`

**ZOrder**
- Fix ZOrder so centerline sits on top of the blue Voronoi paths (when `display_all_possible_paths=True`)
- Centerline sits on top of blue paths when centerline `marker_type="Line"` and `marker_type="Scatter"`

_Bug fixes and README.md edits
Pytests: 180 test_

Feature in Alpha Release:

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

**Find centerline and width of river**
- plotCenterline()
- plotCenterlineWidth()
- riverWidthFromCenterline()
- centerlineVoronoi
- centerlineEqualDistance
- centerlineEvenlySpaced
- centerlineSmoothed
- centerlineLength
- rightBankLength
- leftBankLength

**Export centerline to .CSV and .MAT files**
- saveCenterlineCSV()
- saveCenterlineMAT()

| Centerline | Centerline with Width Lines |
| ------------- | ------------- |
|  |  |


_Pytests: 180 test_

New Features:
**plotCenterline()**
- centerline_type option to graph ("Voronoi", "Evenly Spaced", "Smoothed", "Equal Distance")
- marker_type option to graph (scatter/line)
- centerline_color option (matplotlib color options)

**riverCenterline()**
- ellipsoid option to convert degrees to meters

**plotCenterlineWidth()**
- Replace haversine package with geopy
- Remove unit options (will generate distances in km)
- Fix to prevent lines from being generated outside the polygon

_Bug fixes and README.md edits_
_Pytests: 180 test_

**New Features:**
**centerlineEqualDistance**

- New centerline type that represents equal distances from each points (set by user) and accounts for the radius of the Earth to convert from degrees to meters
- Set by equal_distance optional argument in riverCenterline (defaults to 10 meters)
- Can be saved in saveCenterlineMAT() and saveCenterlineCSV() as `centerline_type="Equal Distance"`

**saveCenterlineMAT**
- Save centerline values to a .mat file

**latitude_header and longitude_header for saveCenterlineMAT and saveCenterlineCSV**

- new options to set the header values for the latitude and longtiude in the output file by the user

_Bug fixes and README.md edits_

_Pytests: 166 tests_

**Bug fixes for returning the width based on centerline**