Prevent upgrade command from succeeding when brew update fails (#80)

@toddblakey recently saw this error when he was running `ih-setup
upgrade`, but it still continued to say it was up-to-date:
```
INFO: Checking for updates...
[email protected]: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
Error: Fetching /usr/local/Homebrew/Library/Taps/consultingmd/homebrew-ih-public failed!
INFO: ih-setup is up-to-date
```

This PR changes it to return early when there's an error running `brew
update` or `brew upgrade ih-core`.

VERSION

@@ -1 +1 @@
-0.1.42
+0.1.43

bin/ih-setup

@@ -301,20 +301,26 @@ function ih::private::state::is-step-installed() {
 }
 
 function ih::private::upgrade() {
-
   ih::log::info "Checking for updates..."
 
+  if ! brew update >/dev/null; then
+    ih::log::error "brew update failed"
+    return 1
+  fi
+
   local OUTDATED
-  brew update >/dev/null
   OUTDATED=$(brew outdated ih-core)
   if [ -z "$OUTDATED" ]; then
     ih::log::info "ih-setup is up-to-date"
     return 0
   fi
 
   ih::log::info "Upgrading ih-setup"
+  if ! brew upgrade ih-core; then
+    ih::log::error "brew upgrade ih-core failed"
+    return 1
+  fi
 
-  brew upgrade ih-core || exit 1
   ih-setup install
 }
 

formula/ih-core.rb

@@ -1,5 +1,5 @@
 class IhCore < Formula
-  VERSION="0.1.42"
+  VERSION="0.1.43"
   desc "Brew formula for installing core tools used at Included Health engineering."
   homepage "https://github.com/ConsultingMD/homebrew-ih-public"
   license "CC BY-NC-ND 4.0"