add tests for most traits; code re-org

Author: ablaom

Project.toml

@@ -6,6 +6,7 @@ version = "0.1.0"
 [deps]
 Distributions = "31c24e10-a181-5473-b8eb-7969acd0382f"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
+IsURL = "ceb4388c-583f-448d-bb30-00b11e8c5682"
 LearnAPI = "92ad9a40-7767-427a-9ee6-6e577f1266cb"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 MLUtils = "f1d291b0-491e-4a28-83b9-f70985020b54"
@@ -21,6 +22,7 @@ UnPack = "3a884ed6-31ef-47d7-9d2a-63182c4928ed"
 [compat]
 Distributions = "0.25"
 InteractiveUtils = "<0.0.1, 1"
+IsURL = "0.2.0"
 LearnAPI = "0.1.0"
 LinearAlgebra = "<0.0.1, 1"
 MLUtils = "0.4"