Update gemspec

Author: domitry

nyaplot.gemspec

@@ -8,15 +8,47 @@ Gem::Specification.new do |spec|
   spec.version       = Nyaplot::VERSION
   spec.authors       = ["Naoki Nishida"]
   spec.email         = ["[email protected]"]
-  spec.summary       = %q{interactive plots generator for Ruby users}
-  spec.description   = %q{interactive plots generator for Ruby users. Visit the GitHub repository to get more information.}
+  spec.summary       = %q{Nyaplot is an interactive plots generator based on Web technology like SVG, WebGL, and JavaScript.}
+  spec.description   = %q{Nyaplot is an Interactive plots generator based on Web technology like SVG, WebGL, and JavaScript. It enables us to create interactive plots interactively on IRuby notebook, a web-based Ruby environment. Nyaplot is totally web-based gem and plots can be embedded into Rails or Sinatra seemlesly. Supported charts include basic 2D plot, 3D plot, Map plot and plot for Biology. See nbviewer (http://nbviewer.ipython.org/github/domitry/nyaplot/blob/master/examples/notebook/Index.ipynb) to overview what plots can be done with nyaplot and how to create them.}
   spec.homepage      = "https://www.github.com/domitry/nyaplot"
   spec.license       = "MIT"
+  spec.post_install_message = <<-EOF
+************************************************************************
+Welcome to Nyaplot
+
+ ___/|
+ \o.O| 
+ (___)
+   U
+
+Thank you for installing Nyaplot gem.
+
+We strongly recommend you to install IRuby, an interactive
+Ruby environment on web browser at the same time.
+
+$ gem install iruby
+
+If you wonder how to use Nyaplot, see /path/to/nyaplot/examples/notebook
+and run `iruby notebook` in the directory.
+You can find these notebook on your browser:
+http://nbviewer.ipython.org/github/domitry/nyaplot/blob/master/examples/notebook/Index.ipynb
+
+You can also use nyaplot without IRuby like /path/to/nyaplot/examples/rb
+or on your browser:
+https://github.com/domitry/nyaplot/tree/master/examples/rb
+
+Feel free to raise Issue or Pull-request on GitHub.
+Most pull-request might be accepted unless it is broken or too destructive.
+
+Enjoy Nyaplot!
+************************************************************************
+EOF
 
   spec.files         = `git ls-files -z`.split("\x0")
   spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
+  spec.required_ruby_version = ">= 1.9"
 
   spec.add_development_dependency "bundler", "~> 1.5"
   spec.add_development_dependency "rake"