Updated code to reflect latest gem interface

Author: 2016rshah

Gemfile

@@ -1,4 +1,4 @@
 source 'http://rubygems.org'
 ruby "2.6.6"
 gem 'sinatra'
-gem 'githubchart', '>= 3.2.0'
+gem 'githubchart', '>= 3.3.1'

Gemfile.lock

@@ -2,10 +2,10 @@ GEM
   remote: http://rubygems.org/
   specs:
     basiccache (1.0.0)
-    githubchart (3.2.0)
-      githubstats (~> 3.1.0)
+    githubchart (3.3.1)
+      githubstats (~> 3.2.0)
       svgplot (~> 1.0.0)
-    githubstats (3.1.0)
+    githubstats (3.2.0)
       basiccache (~> 1.0.0)
       nokogiri (~> 1.10.8)
     mini_portile2 (2.4.0)
@@ -25,7 +25,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  githubchart (>= 3.2.0)
+  githubchart (>= 3.3.1)
   sinatra
 
 RUBY VERSION

app.rb

@@ -18,7 +18,7 @@
     headers 'Cache-Control' => "max-age=#{60*60*24}"
 
     username = params[:username].chomp('.svg') #Chomp off the .svg extension to be backwards compatible
-    svg = GithubChart.new(user: username).svg
+    svg = GithubChart.new(user: username).render('svg')
     stream do |out|
       out << svg
     end
@@ -39,7 +39,7 @@
         scheme = ['#EEEEEE', lighten_color(base_color, 0.3), lighten_color(base_color, 0.2), base_color, darken_color(base_color, 0.8)]
     end
 
-    svg = GithubChart.new(user: username, colors: scheme).svg
+    svg = GithubChart.new(user: username, colors: scheme).render('svg')
     stream do |out|
       out << svg
     end