Fix rake build procedure on downloading HTTPS tarball.

[sho-h]

rake build fails on downloading HTTPS tarball. I met below error.

C:/Ruby21-x64/lib/ruby/2.1.0/net/http.rb:923:in `connect': SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed (OpenSSL::SSL::SSLError)
        from C:/Ruby21-x64/lib/ruby/2.1.0/net/http.rb:923:in `block in connect'
        from C:/Ruby21-x64/lib/ruby/2.1.0/timeout.rb:75:in `timeout'
        from C:/Ruby21-x64/lib/ruby/2.1.0/net/http.rb:923:in `connect'
        from C:/Ruby21-x64/lib/ruby/2.1.0/net/http.rb:863:in `do_start'
        from C:/Ruby21-x64/lib/ruby/2.1.0/net/http.rb:852:in `start'
        from C:/Ruby21-x64/lib/ruby/2.1.0/net/http.rb:583:in `start'
        from C:/Ruby21-x64/lib/ruby/2.1.0/net/http.rb:478:in `get_response'
        from -e:1:in `<main>'

bsdtar in config/railsinstaller.yml, url is "http://downloads.sourceforge.net/mingw/basic-bsdtar-2.8.3-1-mingw32-bin.zip. But bsdtar was redirected to https://downloads.sourceforge.net/project/mingw/MinGW/Extension/bsdtar/basic-bsdtar-2.8.3-1/basic-bsdtar-2.8.3-1-mingw32-bin.zip.

This URL causes OpenSSL::SSL::SSLError like below.

$ ruby -r net/http -r uri -e 'Net::HTTP.get_response(URI.parse("https://downloads.sourceforge.net/project/mingw/MinGW/Extension/bsdtar/basic-bsdtar-2.8.3-1/basic-bsdtar-2.8.3-1-mingw32-bin.zip"))'
C:/Ruby21-x64/lib/ruby/2.1.0/net/http.rb:923:in `connect': SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed (OpenSSL::SSL::SSLError)

I set env var to fix that. I tested with using http://curl.haxx.se/ca/cacert.pem.

[emachnic]

Is this still an issue? Please try with the latest version and open a new PR if needed