Initialise tflint to install plugins (gruntwork-io#62)

Ensure Packer files are validated (gruntwork-io#61)

* Ensure that packer validate is executed on a directory
* Ensure that packer validate is restricted to modern HCL2
  Packer templates and corresponding file suffixes

Add packer validate (gruntwork-io#58)

Clean up PATH after changing it (gruntwork-io#56)

Adding to the path without warning the user seems a little invasive.  
Save the original value and change it back after.

Increase bash script portability (gruntwork-io#54)

Fixes "Executable `/bin/bash` not found" on NixOS systems

Update terraform-fmt to match terraform-validate (gruntwork-io#46)

This PR updates the `terraform-fmt` hook as follows:

1. Run with `-diff -check` so the differences are printed, rather than made on disk.
1. Instead of exiting on the first error, save the exit codes, and print out all `fmt` errors before exiting.

These changes are very similar to gruntwork-io#45.

Merge pull request gruntwork-io#44 from parkalla86/update-shebang-tf-sh

Updated shebang to #!/usr/bin/env bash

Merge pull request gruntwork-io#35 from shmileee/helmlint-serial

Run helmlint hook as single process

Merge pull request gruntwork-io#32 from gruntwork-io/yori-fix-tfvalidate

Fix terraform-validate hook

Merge pull request gruntwork-io#30 from gruntwork-io/pull-request-29

Extend gruntwork-io#29