Generate dummy cross-compile target when no configuration exists.

This fixes issue #16.
Merge pull request #48 from mvz/silence-cross-configuration-warning

Generate dummy cross-compile target when no configuration exists.

Also closes #16
Merge pull request #49 from larskanis/master

Detect 32bit mingw-gcc executable for cross compile
Bump supported versions for testing

Ruby 1.8.7 and Ruby 1.9.2 are the minimum cross-compiled versions
supported.
Update History.txt to reflect latest pull merges
Get rid of RCov
Update development dependencies
Solve deprecations from Cucumber upgrade
Update gemspec dependencies
Prepare for release
Raise error when no make tool was found. Closes #53
Bump version and prepare for release
Do not cache the list of source_files

This allows me to run a task which generates java source files, prior to having rake-compiler compile them.
Merge pull request #64 from sgonyea/master

Remove the caching of source_files
Add note that ExtensionTask param should match create_makefile

Referencing GH-66
Merge pull request #67 from Marketcircle/master

Fix GH-66
Unset variables that can affect cross-compilation. Closes #55

Environment variables like CC, CXX, LDFLAGS, CPPFLAGS and RUBYOPT
might be leaking from user's environment or tools like Bundler.

Unset those to avoid these alter the cross-compilation of Ruby.
Missing changelog
Update feature and related code to remove warnings

Use 1.8.7-p371 and 1.9.3-p327 as base, no longer use 1.9.2
Prepare for release