URL Cleanup (#124)

This commit updates URLs to prefer the https protocol. Redirects are not followed to avoid accidentally expanding intentionally shortened URLs (i.e. if using a URL shortener).

# Fixed URLs

## Fixed Success
These URLs were switched to an https URL with a 2xx status. While the status was successful, your review is still recommended.

* http://stackoverflow.com/questions/1593051/how-to-programmatically-determine-the-current-checked-out-git-branch migrated to:
  https://stackoverflow.com/questions/1593051/how-to-programmatically-determine-the-current-checked-out-git-branch ([https](https://stackoverflow.com/questions/1593051/how-to-programmatically-determine-the-current-checked-out-git-branch) result 200).
* http://stackoverflow.com/questions/29300806/a-bash-script-to-check-if-a-string-is-present-in-a-comma-separated-list-of-strin migrated to:
  https://stackoverflow.com/questions/29300806/a-bash-script-to-check-if-a-string-is-present-in-a-comma-separated-list-of-strin ([https](https://stackoverflow.com/questions/29300806/a-bash-script-to-check-if-a-string-is-present-in-a-comma-separated-list-of-strin) result 200).
* http://www.apache.org/licenses/LICENSE-2.0 migrated to:
  https://www.apache.org/licenses/LICENSE-2.0 ([https](https://www.apache.org/licenses/LICENSE-2.0) result 200).
* http://www.spring.io migrated to:
  https://www.spring.io ([https](https://www.spring.io) result 301).

# Ignored
These URLs were intentionally ignored.

* http://maven.apache.org/POM/4.0.0
* http://maven.apache.org/xsd/maven-4.0.0.xsd
* http://www.w3.org/2001/XMLSchema-instance

mvnw.cmd

@@ -7,7 +7,7 @@
 @REM "License"); you may not use this file except in compliance
 @REM with the License.  You may obtain a copy of the License at
 @REM
-@REM    http://www.apache.org/licenses/LICENSE-2.0
+@REM    https://www.apache.org/licenses/LICENSE-2.0
 @REM
 @REM Unless required by applicable law or agreed to in writing,
 @REM software distributed under the License is distributed on an