Fixed bug in generating distributionUrl

[er-han]

Bug was only in those locales which contain small dotless I letter (ı).
More detail: https://groups.google.com/forum/#!topic/gradle-dev/JHZqo_EJ2zs

Any of the checked boxes below indicate that I took action:

• Reviewed the Contribution Guidelines.
• Signed the Gradle CLA.
• Ensured that basic checks pass: ./gradlew quickCheck

For all non-trivial changes that modify the behavior or public API:

• Before submitting a pull request, I started a discussion on the Gradle developer list,
  the forum or can reference a JIRA issue.
• I considered writing a design document. A design document can be
  brief but explains the use case or problem you are trying to solve,
  touches on the planned implementation approach as well as the test cases
  that verify the behavior. Optimally, design documents should be submitted
  as a separate pull request. Samples
  can be found in the Gradle GitHub repository. Please let us know if you need help with
  creating the design document. We are happy to help!
• The pull request contains an appropriate level of unit and integration
  test coverage to verify the behavior. Before submitting the pull request
  I ran a build on your local machine via the command
  ./gradlew quickCheck <impacted-subproject>:check.
• The pull request updates the Gradle documentation like user guide,
  DSL reference and Javadocs where applicable.

[lacasseio]

Thank you very much for providing a PR for this issue. Would you mind adding a test for this PR just so we don't break this use case in the future?

[er-han]

@lacasseio I have added a test for this bug fix.

[lacasseio]

Thanks for the contribution. I manually merge it as I did a small fixed to the test. We identified that other places in Gradle code base is vulnerable this toLowerCase problem. If you feel strongly about this, we could use your help in improving Gradle. Have a look at issue #1506. We would be looking at adding Findbugs or Pmd check to catch this kind of problem and fixing every occurrence.

[er-han]

I would be glad if I can help in improving Gradle.