Re-use http.Request

[groovili]

Hi!
I've added small optimization and modules support.
The main idea is to re-use http.Request created from params or provided directly and re-create only request.Body from originalBody for retries.
This change simplifies flow.
Also I've changed PostForm because it's mostly the same as Post and can be handled with input params without additional logic.
Tests are passing and no breaking changes.

[sethgrid]

@groovili Thanks for making a PR! Looks like there are merge conflicts that need to be resolved first.

[groovili]

@sethgrid resolved :)

[sethgrid]

@groovili

$ go test
# github.com/sethgrid/pester [github.com/sethgrid/pester.test]
./pester.go:27:64: newline in string
FAIL	github.com/sethgrid/pester [build failed]

Looks like a missing end-quote.

After I added the missing end-quote:

$ go test
--- FAIL: TestCookiesJarPersistence (0.00s)
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x40 pc=0x12bb433]

goroutine 44 [running]:
testing.tRunner.func1.1(0x130bce0, 0x15f1420)
	/usr/local/go/src/testing/testing.go:941 +0x3d0
testing.tRunner.func1(0xc000106b40)
	/usr/local/go/src/testing/testing.go:944 +0x3f9
panic(0x130bce0, 0x15f1420)
	/usr/local/go/src/runtime/panic.go:967 +0x15d
github.com/sethgrid/pester.(*Client).pester(0xc00013e000, 0x136a751, 0x3, 0x136a74e, 0x3, 0x0, 0xc000136040, 0x16, 0x0, 0x0, ...)
	/Users/sethammons/workspace/go/src/github.com/sethgrid/pester/pester.go:346 +0x4c3
github.com/sethgrid/pester.(*Client).Get(...)
	/Users/sethammons/workspace/go/src/github.com/sethgrid/pester/pester.go:436
github.com/sethgrid/pester.TestCookiesJarPersistence(0xc000106b40)
	/Users/sethammons/workspace/go/src/github.com/sethgrid/pester/pester_test.go:580 +0x352
testing.tRunner(0xc000106b40, 0x13841b8)
	/usr/local/go/src/testing/testing.go:992 +0xdc
created by testing.(*T).Run
	/usr/local/go/src/testing/testing.go:1043 +0x357
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x10 pc=0x124df4e]

goroutine 47 [running]:
net/http.(*Client).do(0xc00012e120, 0x0, 0x0, 0x0, 0x0)
	/usr/local/go/src/net/http/client.go:576 +0xae
net/http.(*Client).Do(...)
	/usr/local/go/src/net/http/client.go:567
github.com/sethgrid/pester.(*Client).pester.func2(0xc00013e000, 0xc0001120b0, 0xc0001120c0, 0xc000104900, 0xc00012e120, 0xc0001048a0, 0x136a751, 0x3, 0x136a74e, 0x3, ...)
	/Users/sethammons/workspace/go/src/github.com/sethgrid/pester/pester.go:298 +0x1c2
created by github.com/sethgrid/pester.(*Client).pester
	/Users/sethammons/workspace/go/src/github.com/sethgrid/pester/pester.go:284 +0x4bb
exit status 2
FAIL	github.com/sethgrid/pester	0.053s

Looks like there is still some work to be done.

[groovili]

@sethgrid Sorry, my bad. Did small change after checking tests.
It should be ok now.

[sethgrid]

Thanks for the PR!