Changes

Error if some context keys are missing
Error if any of the emails could not be generated (missing context keys, missing subject or keys with leading underscores)
Try to send as many emails as possible, skipping errors (closes #3)
Rename preview files to HTML (works better with new Chromium versions)
Pass an absolute filepath to browser (works better on Windows)
Update mustache renderer

`bart` binaries

git revision:

2ef5cc62abfe857b43e4ddf352004e3b23691410

Go compiler version:

go version go1.10.3 linux/amd64

SHA256 digest:

bb763eb531904a106236acf7167f1a0da7ff78e7ffe585d15b9db68d1ab29c19  bart

SHA512 digest:

a7125047446b408373a8a3301172fa3c8878f4ef52bb93aef2e520cddb75061f9d120490d5bf1239d06d10846c828d9cb87a7bcc1effa69f8a432239c08c986e  bart

SHA256 digest:

cefa6669c3b6cc6d3aae7fbe62a7f8709a57cb6fa1cf25684a968237c9ccd042  bart

SHA512 digest:

50feeabf8de0dff4ac274cc3445077c0fc7f30e9d96713c562ec673f02b4f65a5f527a050ea40a05c2eda4c68676cedfecda0fe375bee7dd7db6049237967cb8  bart

SHA256 digest:

e08df0b8b2758b64aa12f07a3328ec8fa3998ad0f5a2530a1367bbebf5d9d81e  bart.exe

SHA512 digest:

7ca2664508c7d3a87cee3f00d40f34a3ff24a9aa4494698392d1b24079bf1411f2531d55617d29a7ef472cc556bc0228972ea6505acbb4efb635416d56af3b50  bart.exe