Clean: Change ERROR msg to type WARNING when dynamic library not found.
Issue #775: Add import hook for raven package.
Fix: On Windows we need to keep path C:\Windows\system32;C:\Windows for running created .exe files.
Fix: Unset env. variable VIRUAL_ENV for frozen apps.
Fix: Scipy test case running in virtualenv.
Merge remote-tracking branch 'upstream/develop' into develop

Conflicts:
	PyInstaller/bindepend.py
Clean: Update README.
Clean: Set version to just 2.1.0.
Fix: Links to manual and to changelog in README.
Merge pull request #80 from matysek/develop

Some fixes related to final testing of 2.1 on Windows.