Check for Python 3 by spawning it and checking the output of '--version'

Closes #76.
no semicolons
list: use Array.isArray()
v0.5.1
configure: better python version number parsing

Closes #79.
v0.5.2
configure: a little better python version check

Should fix #82.
v0.5.3
configure: don't use $HOMEDRIVE

It doesn't even represent the value we want (it specifies the drive of the $HOME
dir, not the drive that the system is installed on).

Closes #80.
v0.5.4
initial attempt at symlinking resulting files into the "build" dir
match npm's output for the done "ok" log message
install: semver.lt() returns `null` when false... wtf?
Revert "install: semver.lt() returns `null` when false... wtf?"

This reverts commit fbfbea7d55b4f81661b3e865c183ae9ff104604c.

`null` actually only happens when the 2 versions are equal, haha.
disable symlink behavior for now
log
install: ensure the "error" event is being caught by the node tarball request

This might fix #90.
install: don't start piping download contents until the "response" event
install: require the --nodedir flag to be passed for "pre" versions of node

Fixes #86.
v0.5.5