README: add improvements

Move the README to README.md so Gerrit can render it; currently
Gerrit only renders files named exactly "README.md" (for example at
https://go.googlesource.com/go).

Add more links to the README explaining how to file issues,
how to submit code changes, where to download the code to and
how to get it. Hopefully this should help people who go to
https://go.googlesource.com/text or https://github.com/golang/text
figure out how to get started with development.

Change-Id: I55b6e7dea6fda80513a971e2e4c37b2338edc968
Reviewed-on: https://go-review.googlesource.com/49910
Reviewed-by: Kevin Burke <kev@inburke.com>
diff --git a/README.md b/README.md
index 24be1c6..75e29bc 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,8 @@
+# Go Text
+
 This repository holds supplementary Go libraries for text processing, many involving Unicode.
 
-
-# Semantic Versioning
+## Semantic Versioning
 This repo uses Semantic versioning (http://semver.org/), so
 1. MAJOR version when you make incompatible API changes,
 1. MINOR version when you add functionality in a backwards-compatible manner,
@@ -18,8 +19,12 @@
 A major new CLDR version is mapped to a minor version increase in x/text.
 Any other new CLDR version is mapped to a patch version increase in x/text.
 
+## Download/Install
 
-# Contribute
+The easiest way to install is to run `go get -u golang.org/x/text`. You can
+also manually git clone the repository to `$GOPATH/src/golang.org/x/text`.
+
+## Contribute
 To submit changes to this repository, see http://golang.org/doc/contribute.html.
 
 To generate the tables in this repository (except for the encoding tables),
@@ -40,6 +45,20 @@
 ICU conformance tests (if available). This requires that you have the correct
 ICU version installed on your system.
 
+TODO:
+- updating unversioned source files.
+
+## Generating Tables
+
+To generate the tables in this repository (except for the encoding
+tables), run `go generate` from this directory. By default tables are
+generated for the Unicode version in core and the CLDR version defined in
+golang.org/x/text/unicode/cldr.
+
+Running go generate will as a side effect create a DATA subdirectory in this
+directory which holds all files that are used as a source for generating the
+tables. This directory will also serve as a cache.
+
 ## Versions
 To update a Unicode version run
 
@@ -61,3 +80,12 @@
 So updating to a different version may not work.
 
 The files in DATA/{iana|icu|w3|whatwg} are currently not versioned.
+
+## Report Issues / Send Patches
+
+This repository uses Gerrit for code changes. To learn how to submit changes to
+this repository, see https://golang.org/doc/contribute.html.
+
+The main issue tracker for the image repository is located at
+https://github.com/golang/go/issues. Prefix your issue with "x/image:" in the
+subject line, so it is easy to find.