First stable release

• Cleaned up conan related build code
• Simplified linking of targets
• Expanded on usage examples and explanation of linking in README.md
• Updated the name of member functions writeAttributeToLink() to writeAttribute() to follow naming convention
• New conan repo for h5pp: https://bintray.com/davidace/conan-public/h5pp%3Adavidace
• New DOWNLOAD_METHOD selection method to choose between "none", "conan" and "native" download methods for dependencies
• New conanfile.py recipe added.