Format the possible version formats as a table

Note I: This syntax is supported by MarkdownExtra, which both getcomposer
and github are using.

Note II: This patch currently breaks the PDF, because pandoc does not like
non-standard markdown tables. Ideas for fixing this appreciated.

Note III: The idea for this patch came up a few weeks ago on IRC. We
agreed back then that a table would be a good idea.

Note IIII: This patch creates a stability section which opens the door for
finally documenting how stability works in the composer docs.

doc/01-basic-usage.md

@@ -58,31 +58,31 @@ smaller decoupled parts.
 
 ### Package Versions
 
-We are requiring version `1.0.*` of monolog. This means any version in the `1.0`
+In the previous example we were requiring version `1.0.*` of monolog. This
-development branch. It would match `1.0.0`, `1.0.2` or `1.0.20`.
+means any version in the `1.0` development branch. It would match `1.0.0`,
+`1.0.2` or `1.0.20`.
 
 Version constraints can be specified in a few different ways.
 
-* **Exact version:** You can specify the exact version of a package, for
+Name           | Example               | Description
-  example `1.0.2`.
+-------------- | --------------------- | -----------
+Exact version  | `1.0.2`               | You can specify the exact version of a package.
+Range          | `>=1.0` `>=1.0,<2.0`  | By using comparison operators you can specify ranges of valid versions. Valid operators are `>`, `>=`, `<`, `<=`, `!=`. You can define multiple ranges, separated by a comma, which will be treated as a **logical AND**.
+Wildcard       | `1.0.*`               | You can specify a pattern with a `*` wildcard. `1.0.*` is the equivalent of `>=1.0,<1.1`.
+Tilde Operator | `~1.2`                | Very useful for projects that follow semantic versioning. `~1.2` is equivalent to `>=1.2,<2.0`. For more details, read the next section below.
 
-* **Range:** By using comparison operators you can specify ranges of valid
+### Next Significant Release (Tilde Operator)
-  versions. Valid operators are `>`, `>=`, `<`, `<=`, `!=`. An example range
-  would be `>=1.0`. You can define multiple ranges, separated by a comma:
-  `>=1.0,<2.0`.
 
-* **Wildcard:** You can specify a pattern with a `*` wildcard. `1.0.*` is the
+The `~` operator is best explained by example: `~1.2` is equivalent to
-  equivalent of `>=1.0,<1.1`.
+`>=1.2,<2.0`, while `~1.2.3` is equivalent to `>=1.2.3,<1.3`. As you can see
+it is mostly useful for projects respecting [semantic
+versioning](http://semver.org/). A common usage would be to mark the minimum
+minor version you depend on, like `~1.2` (which allows anything up to, but not
+including, 2.0). Since in theory there should be no backwards compatibility
+breaks until 2.0, that works well. Another way of looking at it is that using
+`~` specifies a minimum version, but allows the last digit specified to go up.
 
-* **Next Significant Release (Tilde Operator):** The `~` operator is best
+### Stability
-  explained by example: `~1.2` is equivalent to `>=1.2,<2.0`, while `~1.2.3` is
-  equivalent to `>=1.2.3,<1.3`. As you can see it is mostly useful for projects
-  respecting [semantic versioning](http://semver.org/). A common usage would be
-  to mark the minimum minor version you depend on, like `~1.2` (which allows
-  anything up to, but not including, 2.0). Since in theory there should be no
-  backwards compatibility breaks until 2.0, that works well. Another way of
-  looking at it is that using `~` specifies a minimum version, but allows the
-  last digit specified to go up.
 
 By default only stable releases are taken into consideration. If you would like
 to also get RC, beta, alpha or dev versions of your dependencies you can do