Resolves issue #179 (https://github.com/alimanfoo/petl/issues/179): search complement

searchcomplement() function has been added.  For code reusability and to implicitly ensure that the function is the complement of search, the implementation is wrapper of search(), and search() has been extended to allow for complement behavior.

search() (and related views and iterator functions) now includes a 'complement_flag' boolean (default=False).  This yields the existing functionality (confirmed with existing unittests).

When complement_flag=True, the iterator function now yields rows that fail the test() lambda function

Docstring modified to describe functionality, mirroring the docstring for search()

unittest added: petl.test.transform.text_regex.test_searchcomplement()
`complement_flag` keyword replaced with `complement` for consistency
modified docstrings to link between search() and searchcomplement()
Update regex.py

Fixed docstring - although "data rose" sounds like something I should buy my wife, we're actually referring to "data rows" here.
Merge pull request #274 from rogerkwoodley/issue-179

closes #179