Bump version to 0.6.0
Add Default instance for BuildFlags
Add doctest test suite
Add documentation and testable example for toBuildPrefix
Development.Shake.Language.C.Target.archString

Fixes #19
Fix wording
Export only two ToolChain functions from the main module

Expose ToolChain module for toolchain writers.
Import Control.Category instead of Control.Arrow when only using >>>

Fixes #18
Fix Haddock markup
Hide Rules module, only export from main module
Record some changes in changelog
Make changelog file uppercase
Add Travis CI configuration file
Add Travis CI build status icon
Refer to hackage documentation instead of the manual

Manual content is now in Haddock documentation.
Add Default instance for PkgConfig options

Remove functions wrappers with default options.
Export Data.Default.Class.def from BuildFlags
Export Linkage and ToolChainVariant from main module
Don't export Data.Default.Class.def from BuildFlags
Add PkgConfig.defaultOptions as an alias for Data.Default.Class.def