refactor(commands): separate commands and its core into two folders (#32)

- I think it would be better if one for commands only, one for the spec
handling core logic so people won't be confused by the core logic inside
the commands folder (cleaner I guess)
- Regen docs

commands/python/streamlit.go

@@ -1,14 +1,14 @@
 package python
 
 import (
-	"github.com/versenilvis/iris/commands/core"
+	"github.com/versenilvis/iris/spec"
 )
 
 func init() {
-	core.Register(&core.Spec{
+	spec.Register(&spec.Spec{
 		Name:        "streamlit",
 		Description: "Streamlit",
-		Subcommands: []core.Subcommand{
+		Subcommands: []spec.Subcommand{
 			{Name: "activate", Description: "Activate Streamlit by entering your email"},
 			{Name: "cache", Description: "Manage the Streamlit cache"},
 			{Name: "clear", Description: "Clear st.cache, st.memo, and st.singleton caches"},
@@ -21,7 +21,7 @@ func init() {
 			{Name: "file", Description: "The Python script to run"},
 			{Name: "version", Description: "Print Streamlit's version number"},
 		},
-		Options: []core.Option{
+		Options: []spec.Option{
 			{Name: "--log_level", Description: "Set the log level"},
 			{Name: "--help", Description: "Show a help message and exit"},
 			{Name: "--version", Description: "Show the version and exit"},