Add tests for `Tester.skip`
Implement `Tester.skip`
Add test results for skipped
Add `casper.thenSkip()`, `casper.thenSkipIf()`...

... and `casper.thenSkipUnless()`
Fix SKIP color.
skipping steps should not mess with assertion number

THis was a mistake as `assertion` is clearly different from `steps`.
`test.skip` does skip steps.
Fix comments in casper module about skip methods

As seen in premvious commit skip does skip steps, no tests.
Decouple Casper `skip` from Tester.

In fact for now the `tester.skip` uses `casper.skip`.
merged PR #405
skipped tests should not affect build final status
refs #405 - renamed Casper#skip to #bypass
Merge branch 'master' into skip
refactored Tester#skip
added more cli tests