faster doc builds and fix redirect on 0.4

ci/after-success.sh

@@ -21,6 +21,7 @@ main() {
         cp LICENSE-* $td/book/$lang/
     done
 
+    local root=$(pwd)
     # build older docs
     for ver in ${vers[@]}; do
         local prefix=${ver%.*}
@@ -32,13 +33,13 @@ main() {
         pushd $src
         cargo doc || cargo doc --features timer-queue
         cp -r target/doc $td/$prefix/api
-        sed 's|URL|rtfm/index.html|g' redirect.html > $td/$prefix/api/index.html
+        sed 's|URL|rtfm/index.html|g' $root/redirect.html > $td/$prefix/api/index.html
         for lang in ${langs[@]}; do
             ( cd book/$lang && mdbook build )
             cp -r book/$lang/book $td/$prefix/book/$lang
             cp LICENSE-* $td/$prefix/book/$lang/
         done
-        sed 's|URL|book/en|g' redirect.html > $td/$prefix/index.html
+        sed 's|URL|book/en|g' $root/redirect.html > $td/$prefix/index.html
         popd
 
         rm -rf $src

ci/install.sh

@@ -1,8 +1,10 @@
 set -euxo pipefail
 
 main() {
+    # these are not needed for doc builds
+    if [ $TRAVIS_BRANCH != master ] || [ $TRAVIS_PULL_REQUEST != false ]; then
         if [ $TARGET = x86_64-unknown-linux-gnu ]; then
-        ( cd .. && cargo install microamp-tools --version 0.1.0-alpha.2 -f )
+            ( cd .. && cargo install microamp-tools --version 0.1.0-alpha.3 -f )
             rustup target add thumbv6m-none-eabi thumbv7m-none-eabi
         fi
 
@@ -12,11 +14,12 @@ main() {
         curl -L https://github.com/japaric/qemu-bin/raw/master/14.04/qemu-system-arm-2.12.0 > qemu/qemu-system-arm
         chmod +x qemu/qemu-system-arm
 
+        pip install linkchecker --user
+    fi
+
     # install mdbook
     curl -LSfs https://japaric.github.io/trust/install.sh | \
         sh -s -- --git rust-lang-nursery/mdbook --tag v0.3.1
-
-    pip install linkchecker --user
 }
 
 main