readme: add more tips/links

Change-Id: Ie4152539a64fe73cbf494809e2f271b5b00bfc85
Reviewed-on: https://weave-review.googlesource.com/2921
Reviewed-by: Alex Vakulenko <avakulenko@google.com>

README.md

diff --git a/README.md b/README.md
index 0d691f3..c640581 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,8 @@
 PATH=~/bin:$PATH
 ```
 
-Download the Repo tool and ensure that it is executable:
+Download the [Repo tool](https://gerrit.googlesource.com/git-repo) and ensure
+that it is executable:
 
 ```
 curl https://storage.googleapis.com/git-repo-downloads/repo > ~/bin/repo
@@ -103,7 +104,7 @@
 
 ```
 make all -j
-````
+```
 
 ### Build library
 
@@ -136,6 +137,10 @@
 
 # Making changes
 
+The [Android Developing site](https://source.android.com/source/developing.html)
+has a lot of good tips for working with git and repo in general.  The tips below
+are meant as a quick cheat sheet rather than diving deep into relevant topics.
+
 ### Configure git
 Make sure to have correct user in local or global config e.g.:
 
@@ -164,4 +169,4 @@
 
 ### Request code review
 
-Go to the url from the output of "repo upload" and add reviewers.
+Go to the url from the output of `repo upload` and add reviewers.