Support writing exotic types. (#22)

* Support writing exotic types.

* Remove Manifest.

Author: evetion

Manifest.toml

@@ -1,7 +1,7 @@
 name = "GeoDataFrames"
 uuid = "62cb38b5-d8d2-4862-a48e-6a340996859f"
 authors = ["Maarten Pronk <git@evetion.nl> and contributors"]
-version = "0.1.3"
+version = "0.1.4"
 
 [deps]
 ArchGDAL = "c9ce4bd3-c3d5-55b8-8973-c0e20141b8c3"
@@ -18,7 +18,8 @@ Tables = "1.2, 1.3, 1.4"
 julia = "1.4"
 
 [extras]
+Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test"]
+test = ["Test", "Dates"]

Project.toml

@@ -6,7 +6,7 @@
 
 Simple geographical vector interaction built on top of [ArchGDAL](https://github.com/yeesian/ArchGDAL.jl/). Inspiration from geopandas.
 
-** this is a beta, it needs polishing **
+** note that reading missing values currently doesn't work **
 
 # Installation
 ```julia