Fix names in docstrings and DeprecationWarnings.

Update a number of docstrings and DeprecationWarnings to refer to
the correct methods or attributes.
Merge pull request #411 from jorgenschaefer/fix-deprecation-docstring-typo

Fix deprecation docstring typo
Always cast pr to er in _follow_statements_imports
Merge pull request #422 from fbergroth/fix-completion-params

Fix completion params
detect buildout and add buildout eggs to sys.path
Merge pull request #403 from mfussenegger/dev_buildout

detect buildout and add buildout eggs to sys.path
Fix package_data '*.pym' paths
Merge pull request #423 from syohex/fix-package_data

Fix package_data '*.pym' paths
Merge pull request #407 from hattya/dev

fix virtualenv support
use del instead of assigning empty iterator
reduce regex searches and compile pattern
reduce loops for finding sub parser
use generator to reduce memory usage
keep white spaces, since code_part contains them