environment: Fix logic around url quoting in zsh >= 5.1

Closes #1015, Fixes #978

Thanks to @Eriner for pointing us in right direction.

The code for this comes from zim. This is the last commit with the code we're using:
537f076603 (diff-30465d78a41f73dc0f6967d3f34d7964)

Note that we need this workaround because we currently support back to
4.3.11.

I believe that originally came from here:
https://github.com/robbyrussell/oh-my-zsh/pull/4473

modules/environment/init.zsh

@@ -9,8 +9,24 @@
 # Smart URLs
 #
 
-autoload -Uz url-quote-magic
-zle -N self-insert url-quote-magic
+# This logic comes from an old version of zim. Essentially, bracketed-paste was
+# added as a requirement of url-quote-magic in 5.1, but in 5.1.1 bracketed
+# paste had a regression. Additionally, 5.2 added bracketed-paste-url-magic
+# which is generally better than url-quote-magic so we load that when possible.
+autoload -Uz is-at-least
+if [[ ${ZSH_VERSION} != 5.1.1 ]]; then
+  if is-at-least 5.2; then
+    autoload -Uz bracketed-paste-url-magic
+    zle -N bracketed-paste bracketed-paste-url-magic
+  else
+    if is-at-least 5.1; then
+      autoload -Uz bracketed-paste-magic
+      zle -N bracketed-paste bracketed-paste-magic
+    fi
+  fi
+  autoload -Uz url-quote-magic
+  zle -N self-insert url-quote-magic
+fi
 
 #
 # General