Use HTTPS, not HTTP, for project line URLs

[ctrueden]

As described in #26, the tidy-maven-plugin currently reverts https: URLs, which are now mandatory, to http: URLs, which cause errors. For example, in Eclipse, with http: URLs, I am seeing:

Multiple markers at this line
- cvc-elt.1.a: Cannot find the declaration of element 'project'.
- schema_reference.4: Failed to read schema document 'bundleentry://260.fwk1924378583/xsd/maven-v4_0_0.xsd', because 1) could not find the document; 2) the document could not be read; 3) the root element of the document is not <xsd:schema>.

Whereas with HTTPS, all is well (apart from a nonfatal warning "No grammar constraints (DTD or XML Schema)").

This PR replaces the behavior with https: URLs in the project tag always.

[slachiewicz]

Namespace must be http, location should be https

[ctrueden]

@slachiewicz OK, so like this?

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">

I confirm that with the above line, Eclipse is happy, and the maven-release-plugin still works. Whereas with all HTTPS, maven-release plugin throws the error:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-release-plugin:2.5.3:prepare (default-cli) on project script-editor: Execution default-cli of goal org.apache.maven.plugins:maven-release-plugin:2.5.3:prepare failed: The namespace xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" could not be added as a namespace to "project": The namespace prefix "xsi" collides with an additional namespace declared by the element -> [Help 1]
[ERROR]

[ctrueden]

After amending my commit to change only the schema location, I see that the tidy-maven-plugin already uses HTTPS for that. So this PR is unnecessary. Sorry for the noise.