Changed 'graph' command to show only installed by default. Prettified
resulting graph.

By default, the `brew graph` command would output a dependency graph for every
formula it knew about. Now it only outputs a dependency graph the for formulas
installed. If you want to see the graph for all formulas, use `brew graph
--all`.

Additionally, the old version of the graph command would filter out any
formulas without depdency connections. The updated version now only does this
if calculating dependencies for all formulas via the `--all` flag.

Finally, the resulting graph has been redesigned to be simpler to read. All
formulas which have no other formulas depending on them (i.e., root nodes) are
aligned to the left. They are also outlined in a light grey box, which is
labelled "Safe to Remove". As implied, all of the formulas in this box can be
safely removed without breaking other installed formulas; all formulas outside
this box have at least one installed formula depending on them. This new graph
style is surpressed if the `--all` flag is used.

Closes Homebrew/homebrew#18282.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Closes Homebrew/homebrew#20364.

Closes Homebrew/homebrew#20318.

Closes Homebrew/homebrew#18753.
Closes Homebrew/homebrew#20358.

Refs Homebrew/homebrew#19182.

This allows formulae which won't build with Tiger's ld to conditionally
request a dependency on the ld64 formula. This modifies the build
environment appropriately, and will only be active on Tiger.

Don't try to untar non-tarred gzips.

When expanding dependencies, repeated deps are treated as equal and all
but the first are discarded when #uniq is called on the resulting array.
However, they may have different sets of options attached, so we cannot
assume they are the same.

After the initial expansion, we group them by name and then create a new
Dependency object for each name, merging the options from each group.

Fixes Homebrew/homebrew#20335.

Closes Homebrew/homebrew#20266.

Fixes installation of e.g. ScriptFileFormula/denominator bottles.

Strip `?` and trailing characters from URL extensions and basenames.

This makes some install methods cleaner, and prevents staging of files
with `?` in the name, as that is a weird character.

Affects 2 formulae in core (though potentially externals will need to be fixed.)

Closes Homebrew/homebrew#20316.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Authors should use `python.standard_caveats` instead.

* Accessor for python.binary
* Made `python.brewed?` more robust if no python found at all
* python.brewed? is more relaxed now and allows older versions
  of the Python formula.
* Only print about wrining sitecustomize.py and distutils.cfg if
verbose and debug.

ScriptFileFormula's use is that it installs whatever was downloaded
to bin; if the install is overridden, there's no benefit over deriving
directly from Formula.

Enumerable#max_by didn't exist in 1.8.6, so linkapps failed on Leopard.