launch_diff: upgraded util to not rely on maven plugin

[rnveach]

To show how #273 should be done, I updated my own script to not rely on maven anymore.
It uses the pure Checkstyle CLI with no updates to patch-diff-report-tool needed and not extra dependencies.

• All install commands where changed to package now.
• github support was removed, should just rely on git.
• added extra code to prevent switching to master as if it was a different branch.
• added branch names and commit ids to final report like groovy scripts.

Here is an example run of the differences for the same PR and config:

Maven: http://rveach.no-ip.org/checkstyle/regression/reports/149/
CLI: http://rveach.no-ip.org/checkstyle/regression/reports/150/

Only real difference is counts for number of files being processed overall. Maven was restricting us to Java only file types while CLI pulls in all files.
No changes in difference reporting. No changes to internal web page acting as interface for user to program.
Slight speed increase as we don't need to copy large quantity of files around (twice) or try to minimize those files. Less output to console too (263kb versus 103kb).

An external change will be needed to switch to using CLI full time. Excludes uses a wildcard match while CLI excludes must be a pattern matching. So all excludes will need to be updated in scope of #273 .

[rnveach]

I am unsure what travis failure is about.

[romani]

Mi be some network issue, restarted.

[romani]

Ones CIs resolved ok to merge.

[rnveach]

@romani TC failure is from releasenotes-builder .
Travis is passing now.

[rnveach]

@romani TC failures look false.
https://teamcity.jetbrains.com/viewLog.html?buildId=1269090&tab=Inspection&buildTypeId=Checkstyle_ContributionIdeaInspectionsPullRequest

Unused import (64)

None of these are true. Eclipse gives me no errors.

Declaration has problems in Javadoc references (9)

All these are exceptions and can be found by the compiler.

Redundant throws clause (Errors) (4)

These exceptions are thrown by the utilities.

[rnveach]

TC has passed after a re-run.