Add go tool pprof import support (#165)

This PR adds support for importing from Google's pprof format, which is a gzipped, protobuf encoded file format (that's incredibly well documented!) The [pprof http library](https://golang.org/pkg/net/http/pprof/) also offers an output of the trace file format, which continues to not be supported in speedscope to date (See #77). This will allow importing of profiles generated by the standard library go profiler for analysis of profiles containing heap allocation information, CPU profile information, and a few other things like coroutine creation information.

In order to add support for that a number of dependent bits of functionality were added, which should each provide an easier path for future binary input sources

- A protobuf decoding library was included ([protobufjs](https://www.npmjs.com/package/protobufjs)) which includes both a protobuf parser generator based on a .proto file & TypeScript definition generation from the resulting generated JavaScript file
- More generic binary file import. Before this PR, all supported sources were plaintext, with the exception of Instruments 10 support, which takes a totally different codepath. Now binary file import should work when files are dropped, opened via file browsing, or opened via invocation of the speedscope CLI.
- Transparent gzip decoding of imported files (this means that if you were to gzip compress another JSON file, then importing it should still work fine)

Fixes #60.

--

This is a [donation motivated](https://github.com/jlfwong/speedscope/issues/60#issuecomment-419660710) PR motivated by donations by @davecheney & @jmoiron to [/dev/color](https://www.devcolor.org/welcome) 🎉

sample/programs/go/.gitignore

@@ -0,0 +1,2 @@
+simple
+server

sample/programs/go/Makefile

@@ -0,0 +1,15 @@
+.PHONY: all clean linux-perf
+
+all: simple server
+
+clean:
+	rm -f simple server
+
+simple: simple.go
+	go build $<
+
+server: server.go
+	go build $<
+
+simple.prof: simple
+	./$< -cpuprofile=$@

sample/programs/go/server.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"log"
+	"fmt"
+	"sync"
+	"time"
+	"net/http"
+)
+
+import _ "net/http/pprof"
+
+// See https://golang.org/pkg/net/http/pprof/ for details
+
+func alpha() {
+	z := 3
+	for i := 0; i < 100000; i++ {
+		z *= 3
+	}
+}
+
+func beta() {
+	z := 3
+	for i := 0; i < 100000; i++ {
+		z *= 3
+	}
+}
+
+func delta() {
+	z := 3
+	for i := 0; i < 100000; i++ {
+		z *= 3
+	}
+	alpha()
+	beta()
+}
+
+func gamma() {
+	z := 3
+	for i := 0; i < 100000; i++ {
+		z *= 3
+	}
+}
+
+
+func main() {
+    // we need a webserver to get the pprof webserver
+    go func() {
+        log.Println(http.ListenAndServe("localhost:6060", nil))
+    }()
+    fmt.Println("hello world")
+    var wg sync.WaitGroup
+    wg.Add(1)
+    go leakyFunction(wg)
+    wg.Wait()
+}
+
+func leakyFunction(wg sync.WaitGroup) {
+    defer wg.Done()
+    s := make([]string, 3)
+    for i:= 0; i < 10000000; i++{
+        alpha()
+        beta()
+        delta()
+        gamma()
+        s = append(s, "magical pandas")
+        if (i % 100000) == 0 {
+            time.Sleep(50 * time.Millisecond)
+        }
+    }
+}

sample/programs/go/simple.go

@@ -0,0 +1,53 @@
+package main
+
+import "flag"
+import "runtime/pprof"
+import "os"
+
+var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file")
+
+func alpha() {
+	z := 3
+	for i := 0; i < 100000; i++ {
+		z *= 3
+	}
+}
+
+func beta() {
+	z := 3
+	for i := 0; i < 100000; i++ {
+		z *= 3
+	}
+}
+
+func delta() {
+	z := 3
+	for i := 0; i < 100000; i++ {
+		z *= 3
+	}
+	alpha()
+	beta()
+}
+
+func gamma() {
+	z := 3
+	for i := 0; i < 100000; i++ {
+		z *= 3
+	}
+}
+
+func main() {
+	flag.Parse()
+	if *cpuprofile != "" {
+		f, _ := os.Create(*cpuprofile)
+		pprof.StartCPUProfile(f)
+		defer pprof.StopCPUProfile()
+	}
+
+	for i := 0; i < 10000; i++ {
+		alpha()
+		beta()
+		delta()
+		gamma()
+	}
+}