Add preliminary 3.7.1 release notes (will need update before release)
Update release notes to match sep. 11 ticket list
DOC-1229: manifestdir no longer required to exist

Edited to reflect that this no longer causes an error as of Puppet 3.7.1.
DOC-1228: documented that $environment can be interpolated only in config_version.

Only relevant page seemed to be config_file_environment.markdown.
Update release notes again

This just adds one ticket, about unnecessary errors when using --tags.
Add introduced-in lists to release notes
Merge branch 'puppet371'