Removed the --delete-conflicting and --ignore-conflicts-at-my-risk options, which have long been deprecated and indicated that they're not used.

Changed the launcher relevant environment variable to SETUPTOOLS_LAUNCHER and it now accepts different strings 'natural' and 'executable', instead of only reflecting a boolean value.

Updated changelog once more to provide a re-assuring narrative about the backward-incompatible changes.

--HG--
extra : histedit_source : a1c329f92ee71a707955e352b63987af9de6e120

--HG--
extra : histedit_source : ef811b339d08652c845c5556fd7e2d0f38ee12df

Allow the test to fail on its own merits rather than failing with a not-so-useful message; removed Python 2.3 support.

Suppress output when checking viability of wget/curl. Fixed viability assignment and Windows platform detection.

Issue #63: Initial implementation of a mechanism for securely bootstrapping setuptools, leveraging system tools for trust validation.

Issue 60: Implemented experimental opt-in support for using native launchers rather than installing launcher executables. My initial experience with this technique has been very positive.

Replaced overly-specific error messages with more general ones for improved cross-implementation compatibility. Fixes #50.

Issue 50: Removed filename and line number from SyntaxErrors returned by invalid_marker. This change simplifies the test and paves the way for supporting PyPy.