Integrated: Fixed tidy errors

[Jesper Wilhelmsson]

Fixed some errors found by tidy, and added a make target to run tidy on the generated index.html

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Commit messages:
 - Fixed tidy errors

Changes: https://git.openjdk.java.net/guide/pull/41/files
 Webrev: https://webrevs.openjdk.java.net/?repo=guide&pr=41&range=00
  Stats: 25 lines in 2 files changed: 5 ins; 0 del; 20 mod
  Patch: https://git.openjdk.java.net/guide/pull/41.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/41/head:pull/41

PR: https://git.openjdk.java.net/guide/pull/41