add mruby-enum-lazy mrbgem for Enumerable::Lazy
Hash#replace to preserve order; close #2001
protect NoMethodError from calling to_hash in ==/eql?; close #2002
call to_hash before replacing hash
implement Hash#initialize in C
merge test code from #2003
simplify string equality check
Hash#replace should copy default as well; close #2004
backslash escapes in regexp should be addressed by Regexp processor; close #2005
Refactor MRuby::Gem::List#check.
* Create mrbgem table before dependencies check.
* Topoligical sort gem list.
* Check circular mrbgem dependency.
Merge pull request #2006 from take-cheeze/tsort_dep

Refactor MRuby::Gem::List#check.
Update mruby-head installed on Travis CI

This way other projects can test against it.
Merge pull request #2008 from rkh/patch-1

Update mruby-head installed on Travis CI
Fix ObjectSpace.count_objects document.
Merge pull request #2013 from take-cheeze/objectspace

Fix ObjectSpace.count_objects document.
Fix 'make test' fail to build on Windows(MSVC)
Merge pull request #2014 from kyab/fix_msvc_build_test

Fix 'make test' fail to build on Windows(MSVC)
Merge remote-tracking branch 'upstream/master' into ext