Fixed a docstring mistake.
@bugfix catch error if no .gitignore is found.
@bugfix More gracefull handling of bad pipe input.
New subpackage pygt.reader.

The point of turning reader into a subpackage is to keep all subclasses
of BaseReader organised when I start adding support for new languages.
Minor change in BaseReader.grep_for().
Extracted search related code to pygt/searcher.py.
Minor change. FILE_PATTERNS -> file_patterns.
Delegated some work from Searcher._grep_cmd() to Searcher._get_exclds().
I decided that Searcher._get_exclds() should be public.
Additional debug info: excluded files/dirs.
Moved unless unittest code out of the way till later.
Some pylint suggestions in pygt/searcher.py.
@bugfix Searcher.get_exclds() should return [], [] if there's no .gitignore
More pylint changes, mostly comments/docstrings.
Merge branch 'refactor/reader' into develop
Removed unused import.
Broke up Greptools.__init__() based on pylint suggestion.
Minor pylint suggestions.
More robust implementation of Searcher._get_exclds().
Full grep command is printed if -d flag is set.