Update README with build instructions, fixes #132

README.md

diff --git a/README.md b/README.md
index 94c4f94..7890c50 100644
--- a/README.md
+++ b/README.md
@@ -74,8 +74,11 @@
 
 To build from source you can:
 
-1. Clone this repository and change directory into it
-2. Run `make bootstrap`
+1. Clone this repository into `$GOPATH/src/github.com/Masterminds/glide` and
+   change directory into it
+2. Ensure that the environment variable GO15VENDOREXPERIMENT is set, f.ex. by
+   running `export GO15VENDOREXPERIMENT=1`
+3. Run `make bootstrap`, followed by `make build`
 
 This will leave you with `./glide`, which you can put in your `$PATH` if
 you'd like. (You can also take a look at `make install` to install for