Use newer build tools package.

tannewt · tannewt · commit 0e388d9f7ef6 · 2017-12-26T10:42:17.000-08:00
diff --git a/requirements.txt b/requirements.txt
@@ -1 +1 @@
-circuitpython-travis-build-tools
+circuitpython-build-tools

Original file line number	Diff line number	Diff line change
`@@ -1 +1 @@`
`1`		`-circuitpython-travis-build-tools`
	`1`	`+circuitpython-build-tools`