v2.1.1706216: Docker build fixes & perl locale fix (#89)

* updated Docker build to fix perl locale problem

* found dependency issues that had broken the Docker build
so fixed them too

* changed the build so example FASTA files are copied from
the repo where the docker build is done (so that if these files are
changed in a branch/tag, that's reflected in the image that is built
rather than always referring back to the master branch on github)

* remove path-help email from Dockerfile, in line with PR #88

Co-authored-by: Tim Stickland <ts24@sanger.ac.uk>