Improvements for REPL-driven development

This commit does the following:

* Adds a gitignore for `dev/user.clj` so that developers can create
  a file there w/o worrying about it getting tracked in VCS
* Modifies `dev/user-repl.clj` so that developers can override the
  default REPL Puppet Server config settings in their own `user`
  namespace.
* Provides an example `user.clj.sample` file, which can be copied
  to `user.clj`, which has an example of how to override the
  config settings plus a convenience function for loading the
  `user-repl` namespace and launching Puppet Server.
* Modify `project.clj` to define `user` as the default REPL
  namespace.
(SERVER-137) optimize /certificate_statuses

Deserialize the CRL from disk only once per request to
/certificate_statuses, instead of doing it for each certificate on disk.
Remove production warning from README
Update reference to minimum puppet version to 3.7.3
(MAINT) Update puppet version references to 3.7.3
Merge pull request #263 from waynr/maint

(MAINT) Update puppet version references to 3.7.3
(SERVER-120) Update version to 0.4.0 for release
(SERVER-120) Update CHANGELOG for 0.4.0 release notes

Contains changelog updates for the release summary.
Merge pull request #266 from nwolfe/svr120-release-notes

(SERVER-120) Update CHANGELOG for 0.4.0 release notes
Merge pull request #265 from nwolfe/svr120-update-version-number

(SERVER-120) Update version to 0.4.0 for release
(SERVER-120) Bump version to SNAPSHOT
Merge pull request #267 from nwolfe/svr120-snapshot-version

(SERVER-120) Bump version to SNAPSHOT
DOC-1281 Revised Puppet Server configuration.markdown

Revision + edits.
Squashed commits.
DOC-1289: Puppet Server known_issues page

A few small edits... nothing major here.
DOC-1281 Edited Puppet Server install_from_packages page

Revised the Puppet Server Install from Packages page.
DOC-1281: Puppet Server install_from_packages page

A few more edits.
DOC-1281: Puppet Server install_from_packages
(SERVER-136) Add docs for http client SSL config
(SERVER-136) add link to oracle docs for cipher suites
Merge pull request #256 from cprice404/maint/master/SERVER-136-docs-for-http-client-ssl-config

(SERVER-136) Add docs for http client SSL config