pin knife-rackspace to 0.9.0 or higher

we require --ssh-keypair to be available, which was introduced in
[v0.9.0](https://github.com/opscode/knife-rackspace/blob/master/CHANGELOG.md#v090).

Author: Matthew Fisher

Gemfile

@@ -6,5 +6,5 @@ gem 'foodcritic'
 gem "berkshelf", "~> 2.0.10"
 
 gem 'knife-ec2'
-gem 'knife-rackspace'
+gem 'knife-rackspace', '~> 0.9.0'
 gem 'knife-digital_ocean'

Gemfile.lock

@@ -25,7 +25,7 @@ GEM
     buff-config (0.4.0)
       buff-extensions (~> 0.3)
       varia_model (~> 0.1)
-    buff-extensions (1.0.0)
+    buff-extensions (0.5.0)
     buff-ignore (1.1.1)
     buff-ruby_engine (0.1.0)
     buff-shell_out (0.1.1)
@@ -66,22 +66,21 @@ GEM
       winrm (~> 1.1.2)
     erubis (2.7.0)
     eventmachine (1.0.3)
-    excon (0.25.3)
+    excon (0.31.0)
     faraday (0.8.9)
       multipart-post (~> 1.2.0)
     faraday_middleware (0.9.0)
       faraday (>= 0.7.4, < 0.9)
     ffi (1.9.3)
-    fog (1.15.0)
+    fog (1.20.0)
       builder
-      excon (~> 0.25.0)
+      excon (~> 0.31.0)
       formatador (~> 0.2.0)
       mime-types
       multi_json (~> 1.0)
       net-scp (~> 1.1)
       net-ssh (>= 2.1.3)
-      nokogiri (~> 1.5)
-      ruby-hmac
+      nokogiri (>= 1.5.11)
     foodcritic (0.2.0)
     formatador (0.2.4)
     gssapi (1.0.3)
@@ -101,13 +100,12 @@ GEM
       chef (>= 10.18)
       digital_ocean (~> 1.3.0)
       highline
-    knife-ec2 (0.6.6)
+    knife-ec2 (0.6.4)
       chef (>= 0.10.10)
-      fog (~> 1.15.0)
-      knife-windows (>= 0.5.12)
-    knife-rackspace (0.8.4)
+      fog (~> 1.6)
+    knife-rackspace (0.9.0)
       chef (>= 0.10.10)
-      fog (~> 1.12)
+      fog (~> 1.16)
       knife-windows
     knife-windows (0.5.15)
       em-winrm (~> 0.5, >= 0.5.4)
@@ -174,7 +172,6 @@ GEM
       solve (>= 0.4.4)
       varia_model (~> 0.1)
       winrm (~> 1.1.0)
-    ruby-hmac (0.4.0)
     rubyntlm (0.1.1)
     savon (0.9.5)
       akami (~> 1.0)
@@ -214,4 +211,4 @@ DEPENDENCIES
   foodcritic
   knife-digital_ocean
   knife-ec2
-  knife-rackspace
+  knife-rackspace (~> 0.9.0)