Update Slogger, had to update bundles / missing gems? rmagick ?

[mcdent]

Hi,
Last night I decided to update Slogger. (OS X 10.11)
I downloaded the zip and copied it over my slogger folder as instructed.
A quick check with ./slogger -v and I got:

Mikes-iMac2:Slogger mike$ ./slogger -v
Could not find gem 'rmagick (= 2.13.2)' in any of the gem sources listed in your Gemfile or available on this machine.
Run `bundle install` to install missing gems.

So I tried as instructed:

Mikes-iMac2:Slogger mike$ sudo bundle install
Don't run Bundler as root. Bundler can ask for sudo if it is needed, and installing your bundle as root will break this
application for all non-root users on this machine.
Fetching gem metadata from https://rubygems.org/..........
Fetching version metadata from https://rubygems.org/...
Fetching dependency metadata from https://rubygems.org/..
Resolving dependencies...
Rubygems 2.0.14 is not threadsafe, so your gems will be installed one at a time. Upgrade to Rubygems 2.1.0 or higher to enable parallel gem installation.
Using rake 10.3.2
Using addressable 2.3.6
Using buttock 0.2.0
Using safe_yam 1.0.3
Using thread_safe 0.3.4
Using diff-lcd 1.2.5
Using digest 0.0.1
Using equaliser 0.0.9
Using multipart-post 2.0.0
Using apricot 0.8.6
Using simple-rss 1.3.1
Using hash 3.3.1
Using http_parser.rb 0.6.0
Using multi_son 1.10.1
Using son 1.8.1
Using mime-types 2.3
Using mini_portile 0.6.0
Using multi map 1.1.3
Using oath 0.4.7
Using rack 1.5.2
Installing rmagick 2.13.2 with native extensions

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
checking for Ruby version >= 1.8.5... yes
checking for xcrun... yes
checking for Magick-config... yes
checking for ImageMagick version >= 6.4.9... yes
checking for HDRI disabled version of ImageMagick... yes
/usr/local/bin/Magick-config: line 41: pkg-config: command not found
/usr/local/bin/Magick-config: line 47: pkg-config: command not found
/usr/local/bin/Magick-config: line 50: pkg-config: command not found
/usr/local/bin/Magick-config: line 53: pkg-config: command not found
checking for stdint.h... yes
checking for sys/types.h... yes
checking for wand/MagickWand.h... no

Can't install RMagick 2.13.2. Can't find MagickWand.h.
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
    --with-opt-dir
    --without-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby


Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/rmagick-2.13.2 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/gems/rmagick-2.13.2/ext/RMagick/gem_make.out
Using spec-support 3.1.1
Using simple_auth 0.2.0
Using tilt 1.4.1
Using sqlite3 1.3.11
Using var 2.9.3
Using bundler 1.11.2
Using crack 0.4.2
Using descendants_tracker 0.0.4
Using memorable 0.4.2
Using faraday 0.9.0
Using feed-normaliser 1.5.2
Using http 0.5.1
Using nokogiri 1.6.3.1
Using twitter_auth 0.4.94
Using rack-protection 1.5.3
An error occurred while installing rmagick (2.13.2), and Bundler cannot continue.
Make sure that `gem install rmagick -v '2.13.2'` succeeds before bundling.
Mikes-iMac2:Slogger mike$ 

I must admit I did a bit of searching around and couldn't come up with an obvious solution. I'm pretty sure I didn't have this issue when I first installed Slogger but that was some time ago and more then likely on OS X 10.10.x

Any help is very welcome.
Thanks
Mike