[JENKINS-21557] Possibly too wide table on summary page

- Width of table on summary page depends on other areas of the page. If there is e.g. long message in a commit log, the table will be very wide.
- It seems the default table width is set to 100% in CSS, change to "auto" helps.
- Tested in Chrome, Firefox and Opera.
Merge pull request #31 from mixalturek/master

[JENKINS-21557] Possibly too wide table on summary page