Improve docker file
Improve docker file

 * put global Gemfile into /support
 * install nano
 * set nano as editor

bastilian/Quick-Start-Rails-and-Ruby,vienna-rb/Quick-Start-Rails-and-Ruby,vienna-rb/Quick-Start-Rails-and-Ruby,vienna-rb/Quick-Start-Rails-and-Ruby,bastilian/Quick-Start-Rails-and-Ruby,bastilian/Quick-Start-Rails-and-Ruby,vienna-rb/Quick-Start-Rails-and-Ruby,bastilian/Quick-Start-Rails-and-Ruby