Add support for additional types (MultiLineString, [Multi]Polygon, FeatureCollection)

[anandthakker]

• MultiLineString
• (Multi)Polygon
• FeatureCollection

Closes #1
Closes #2

[tmcw]

While we're at it, I do kind of think that a Point should have a length of 0, rather than throwing an error...

[morganherlocker]

Hm, I'm a bit split on polys and points. The length of both is closer to N/A than 0 in my opinion. I would think that someone sending a polygon or a point at this function is not using it as intended. Not a huge deal either way, but I tend to shy away from supporting more geometry types than necessary.

[anandthakker]

@morganherlocker I'm totally neutral on the Point point, but I feel like getting perimeters of polygons is a reasonable use case. (In fact, it's the one that prompted this PR.) On the other hand, 'line distance' and perimeter aren't obviously the same thing... assuming you think polygon perimeters are a legit enough use case, would you prefer to have that be a separate module?