Port before_v0.60/math, before_v0.60/parsing and before_v0.60/git (#844)

This PR is part of porting all old scripts #221 and includes a set of
small modules:
- `math`
- `parsing`
- `git`

modules/parsing/sample_andres.nu

@@ -0,0 +1,21 @@
+def look_for [word] {
+  open sample_andres.json |
+    flatten |
+    flatten |
+    insert comp {
+        get shoes_name |
+            split row " " |
+            enumerate | each {
+        [[idx, loc]; [$in.index, ($in.item | str index-of $word)]]
+        } | flatten
+    } |
+    flatten |
+    where comp.loc >= 0 |
+    flatten |
+    update idx { $in + 1 } |
+    reject name price loc |
+    rename nameWords targetWordIndex
+}
+
+print (look_for "leather" | to json --indent 4)
+print (look_for "low-top" | to json --indent 4)