Fix pycall dependency

Author: mrkn

Gemfile

@@ -2,5 +2,3 @@ source 'https://rubygems.org'
 
 # Specify your gem's dependencies in matplotlib.gemspec
 gemspec
-
-gem 'pycall', github: 'mrkn/pycall', branch: 'rewrite'

matplotlib.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "pycall", ">= 1.0.0.alpha.20170905"
+  spec.add_dependency "pycall", ">= 1.0.0"
 
   spec.add_development_dependency "bundler", "~> 1.13"
   spec.add_development_dependency "rake", "~> 10.0"