Update README with import instructions and how to build / test (#505)

* update README with import instructions and how to build / test

* fix typo

* remove building the code section from README.md

* add clone instructions to CONTRIBUTING.md

Co-authored-by: Joshua MacDonald <jmacd@users.noreply.github.com>
Co-authored-by: Rahul Patel <rahulpa@google.com>

CONTRIBUTING.md

@@ -13,6 +13,12 @@ join the meeting or get in touch on
 
 ## Development
 
+You can view and edit the source code by cloning this repository:
+
+```bash
+git clone https://github.com/open-telemetry/opentelemetry-go.git
+```
+
 There are some generated files checked into the repo. To make sure
 that the generated files are up-to-date, run `make` (or `make
 precommit` - the `precommit` target is the default).

README.md

@@ -19,14 +19,17 @@ Libraries that produce telemetry data should only depend on `api`
 and defer the choice of the SDK to the application developer. Applications may
 depend on `sdk` or another package that implements the API.
 
-To install the API and SDK packages,
+All packages are published to [go.opentelemetry.io/otel](https://pkg.go.dev/go.opentelemetry.io/otel) and is the preferred location to import from.
 
-```
-$ go get -u go.opentelemetry.io/otel
-```
+Additional resources:
+
+- [Developing using Go Modules](https://blog.golang.org/using-go-modules)
+- [Adding dependencies and installing them](https://golang.org/cmd/go/#hdr-Add_dependencies_to_current_module_and_install_them)
 
 ## Quick Start
 
+Below is a brief example of importing OpenTelemetry, initializing a tracer and creating some simple spans.
+
 ```go
 package main