Fixes #29

Adds the functionality equivalent of the --include-prerelease flag that will allow for including prerelease versions by default defined in the node semver repo here . The feature is accessible through a new method Semver.satisfies(String range, boolean includePrerelease). All public methods will have include-prerelease default to false to maintain backwards compatibility.

Some of the processors are updated to be able to handle advanced ranges properly, as discussed in this issue. Architecturally, Processor is changed from an interface to an abstract class to better handle some common state.

To include proper support for --include-prerelease, we need to add some additional logic for appending a prerelease identifier to certain ranges. For example, by default, 1.x gets translated to >=1.0.0 <2.0.0. If we just used this same exact logic when considering prereleases, it will not work — 1.0.0-beta will not satisfy the range, and 2.0.0-beta will. So the actual correct range would then be >=1.0.0-0 <2.0.0-0, where 0 is the lowest possible prerelease identifier.
However, note that we cannot just change the range to always be >-1.0.0-0 <2.0.0-0, because that would mean anything with a prerelease identifier would satisfy the range, even if --include-prerelease is not set. This has to do with how prerelease versions interact with comparators, as defined here.

Something else that might be noticed is that, with --include-prerelease, ^1.2.3 translates to >=1.2.3 <2.0.0-0, whereas ^1.2 translates to >=1.2.3-0 <2.0.0-0. This has to do with how x ranges are defined. Specifically, the definition is that:

• A missing patch version will be a range that matches the major and minor version
• A missing minor version will be a range that matches the major version

By this logic then, the lowest version that satisfies 1.2.3 is just 1.2.3 (it just so happens to be the only version that satisfies that range, since a range that is a version is just satisfied by the version), while the lowest version that satisfies 1.2 is 1.2.0-0. This is why in Tilde, Caret, and Hyphen ranges, we have the lower bound of the range use the 0 prerelease identifier if a minor or patch version is not specified.