Remove contrib.flow

It's not tested, and sure enough, a glance at the code suggests that `case` and `switch` will evaluate their first argument once for every clause, which is unlikely to be desirable. I say remove it, but if anybody wants to fix and test and re-add `case` (and change it to a square-bracket syntax like `cond`), be my guest.

docs/contrib/flow.rst

@@ -1,58 +0,0 @@
-==========
-Flow
-==========
-
-.. versionadded:: 0.10.1
-
-The ``flow`` macros allow directing the flow of a program with greater ease.
-
-
-Macros
-======
-
-.. _case:
-.. _switch:
-
-case
------
-
-``case`` allows you to decide based on the value of a variable.
-
-
-Usage: `(case variable val1 (body1) val2 (body2) ...)`
-
-Example:
-
-.. code-block:: hy
-
-    (require [hy.contrib.flow [case]])
-
-    (defn temp-commenter [temp]
-        (case temp
-            -10 (print "It's freezing. Turn up the thermostat!")
-            15 (print "Sounds about average.")
-            45 (print "Holy smokes. It's hot in here!")
-               (print  "I don't even know.")))
-
-
-switch
------
-
-``switch`` allows you to run code based on the value of a variable.
-A final extra body allows for a default case.
-
-
-Usage: `(switch var (cond1) (body1) (cond2) (body2) ... )`
-
-Example:
-
-.. code-block:: hy
-
-    (require [hy.contrib.flow [switch]])
-
-    (defn temp-commenter [temp]
-        (switch temp
-            (<= 10.0) (print "Better wear a jacket!")
-            (<= 25.0) (print "Brace yourselves. Summer is coming!")
-            (<= 30.0) (print "Time to get some ice cream.")
-                      (print "Sounds like a heat wave")))

docs/contrib/index.rst

@@ -11,7 +11,6 @@ Contents:
 .. toctree::
    :maxdepth: 3
 
-   flow
    loop
    multi
    profile

hy/contrib/flow.hy

@@ -1,24 +0,0 @@
-;; Additional flow macros
-
-
-(defmacro/g! switch [variable &rest args]
-  (setv g!comp (car args))
-  (setv g!body (car (cdr args)))
-  (setv g!rest (cdr (cdr args)))
-  (setv g!cond `(~(car g!comp) ~variable ~@(cdr g!comp)))
-  (if g!rest
-      (if (cdr g!rest)
-        `(if ~g!cond ~g!body (switch ~variable ~@g!rest))
-        `(if  ~g!cond ~g!body ~@g!rest))
-      `(if  ~g!cond ~g!body)))
-
-(defmacro/g! case [variable &rest args]
-  (setv g!value (car args))
-  (setv g!body (car (cdr args)))
-  (setv g!rest (cdr (cdr args)))
-  (setv g!cond `(= ~variable ~g!value))
-  (if g!rest
-      (if (cdr g!rest)
-        `(if ~g!cond ~g!body (case ~variable ~@g!rest))
-        `(if  ~g!cond ~g!body ~@g!rest))
-      `(if  ~g!cond ~g!body)))