Load .powconfig as well

This is slightly different than how pow uses .powconfig. It uses it to
configure itself via env variables but puma-dev has a bunch of command
line options to do that instead.

So we still load it because folks use .powconfig as a way to set
variables that are used in all apps, but the POW_* variables won't have
any effect at present.

src/puma/dev/app.go

@@ -181,6 +181,10 @@ func (a *App) UpdateUsed() {
 }
 
 const executionShell = `# puma-dev generated at runtime
+if test -e ~/.powconfig; then
+	source ~/.powconfig
+fi
+
 if test -e .env; then
 	source .env
 fi