update gemspec info (add author, gitlab repo)

excelsior.gemspec

@@ -7,13 +7,13 @@ require 'excelsior/version'
 Gem::Specification.new do |spec|
   spec.name          = 'excelsior'
   spec.version       = Excelsior::VERSION
-  spec.authors       = ['Immanuel Häussermann']
-  spec.email         = ['hai@panter.ch']
+  spec.authors       = ['Immanuel Häussermann', 'Alexis Reigel']
+  spec.email         = ['hai@panter.ch', 'lex@panter.ch']
 
   spec.summary       = 'Helps you import data from an excel sheet'
   spec.description   = 'Provides a concise DSL to map, validate and import data ' \
                        'from an excel sheet into your ruby app'
-  spec.homepage      = 'http://github.com/manufaktor/excelsior'
+  spec.homepage      = 'https://git.panter.ch/open-source/excelsior'
   spec.license       = 'MIT'
 
   spec.files         = `git ls-files -z`.split("\x0").reject do |f|