modena@makoto 17:38:24/140213(..git-work/charlock_holmes)% gem install charlock_holmes        
ERROR:  While executing gem ... (NoMethodError)
    undefined method `empty?' for nil:NilClass

これ素敵 ここで出ているらしいです。
Following line is the point saying above message:

--- /usr/pkg/lib/ruby/2.0.0/rubygems/installer.rb.orig	2013-12-20 23:27:31.000000000 +0900
+++ /usr/pkg/lib/ruby/2.0.0/rubygems/installer.rb	2014-02-13 17:47:10.000000000 +0900
@@ -572,7 +572,7 @@
     # the system gem directory, then use the system bin directory, else create
     # (or use) a new bin dir under the gem_home.
     @bin_dir             = options[:bin_dir] || Gem.bindir(gem_home, @install_root)
-    if not @install_root.empty?
+    if not @install_root.nil?
       @bin_dir = File.join(@install_root, @bin_dir)
     end
     @development         = options[:development]

こうしておくと、進みます (blank? でも undefined method になります)
Above patch let me proceed

Successfully installed charlock_holmes-0.6.9.4
Parsing documentation for charlock_holmes-0.6.9.4
Parsing sources...
unable to convert "\xA0" from ASCII-8BIT to UTF-8 for lib/charlock_holmes/charlock_holmes.so, skipping
100% [ 5/ 5]  lib/charlock_holmes/version.rb                                    
Installing ri documentation for charlock_holmes-0.6.9.4
1 gem installed

--- ./libv8-3.11.8.17/ext/libv8/builder.rb.orig 2014-02-13 18:10:08.000000000 +0900
+++ vendor/bundle/ruby/2.0.0/gems/libv8-3.11.8.17/ext/libv8/builder.rb	2014-02-13 18:21:20.000000000 +0900
@@ -45,10 +45,10 @@
       # at the head of PATH. That way all commands that inherit this environment
       # will use ./python -> python2
       if python_version !~ /^2/
-        unless system 'which python2 2>&1 > /dev/null'
+        unless system 'which python2.7 2>&1 > /dev/null'
           fail "libv8 requires python 2 to be installed in order to build, but it is currently #{python_version}"
         end
-        `ln -fs #{`which python2`.chomp} python`
+        `ln -fs #{`which python2.7`.chomp} python`
         ENV['PATH'] = "#{File.expand_path '.'}:#{ENV['PATH']}"
       end
     end

Above makes no change, then,

modena@makoto 18:30:41/140213(..wip/gitlab)% \
sudo ln  /usr/pkg/bin/python2.7 /usr/pkg/bin/python

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.
    /usr/pkg/bin/ruby200 extconf.rb 
creating Makefile
Compiling v8 for x64
Using python 2.7.6
Using compiler: /usr/bin/g++
cc1plus: warnings being treated as errors
../src/flags.cc: In function 'char* v8::internal::SkipWhiteSpace(char*)':
../src/flags.cc:459:24: error: array subscript has type 'char'
../src/flags.cc: In function 'char* v8::internal::SkipBlackSpace(char*)':
../src/flags.cc:465:24: error: array subscript has type 'char'
gmake[1]: ***
[/home/git/gitlab/vendor/bundle/ruby/2.0.0/gems/
   libv8-3.11.8.17/vendor/v8/out/x64.release/obj.target/v8_base/src/flags.o]
Error 1
gmake: *** [x64.release] Error 2

modena@makoto 22:34:11/140213(..wip/gitlab)% 
sudo gem install libv8 -v '3.16.14.3' -- --with-system-v8
Password:
Building native extensions with: '--with-system-v8'
This could take a while...
Successfully installed libv8-3.16.14.3
Parsing documentation for libv8-3.16.14.3
Installing ri documentation for libv8-3.16.14.3
1 gem installed