Refactor install scripts

- Support emacs installation
- Export DOTFILES env var to simplify setup.
- Change filenames for consistency

configs/setup

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+
+dotfiles_path="${HOME}/dotfiles"
+configs_dir="${dotfiles_path}/configs"
+shared_configs="${configs_dir}/shared"
+
+if [[  $(uname) == 'Darwin' ]]; then
+    os_specific_configs="${configs_dir}/os_x"
+elif [[ $(uname) == 'Linux' ]]; then
+    os_specific_configs="${configs_dir}/linux"
+fi
+
+
+function symlink_configs () {
+    configs_dir=$1
+
+    for cf in $(find $configs_dir -type f -name ".*"); do
+        filename=$(grep -o "[^\/]+$" <<<$cf)
+        echo "$filename: "
+
+        if [ -f "${HOME}/${filename}" ] && [ ! -L "${HOME}/${filename}" ]; then
+            echo -n "Backing up ${filename}... " && \
+            mv "${HOME}/${filename}" "${HOME}/${filename}.bak" && \
+            echo "Done."
+        fi
+
+        if [ -L "${HOME}/${filename}" ]; then
+            if [ $(readlink "${HOME}/${filename}") = $cf ]; then
+                echo "Already properly symlinked to ${configs_dir}."
+            else
+                echo "Already symlinked but NOT to the proper location. Aborting..."
+            fi
+        else
+            echo -n "Symlinking to ${filename}... " && \
+            ln -s $cf "${HOME}/${filename}" && \
+            echo "Done."
+        fi
+        echo ""
+    done
+}
+
+
+# handle shared configs
+symlink_configs $shared_configs
+
+# handle os-specific configs
+symlink_configs $os_specific_configs