Remove -Z no-trans support and update tests

Remove support for -Z no-trans on-save checking (fixes #281).
Update some tests for latest nightly.
Pin nightly and clippy to a known-good version for Travis. This should
ensure that minor issues don't cause unrelated PRs to fail. This also
configures the beta/nightly jobs to allow failure. I have a cron job on my
own repository set up so I will be notified whenever things break, and I'll
send PRs when necessary.

Compiler suggestions and message themes + syntax updates

compiler suggestions and message themes
#267

Union has been added to the Syntax
#260

more formatting macros to syntax checking
#258

Compiler suggestions and message themes + syntax updates

compiler suggestions and message themes
#267

Union has been added to the Syntax
#260

more formatting macros to syntax checking
#258

Syntax highlights and bug fixes

switch build syntax to yaml, tests added
Add support for checking tests in Rust 1.23
Readme Updates
Fix example RUST_BACKTRACE environment variable template
Highlight let, static, const as storage.type.rust

Add support for checking tests in Rust 1.23

Add support for checking tests in Rust 1.23

Syntax updates

match large format specs
a few small syntax checking improvements

Updates to Message Handling

Readme updates
Update message handling for Rust 1.24

• All paths are now relative to the workspace root instead of the package root.
• Columns reported in macros are now 1-based (affects test output).

Support or new JSON formats and autocomplete on ::

Support new suggestion JSON format introduced in 1.23/1.24.
Fix some duplicate messages being displayed.
Update tests for minor wording changes in some diagnostics.
Update tests to handle debug files being produced in 1.21.
Support multi-span messages added in 1.21.
Autocomplete support for path separators (::)

As always excellent work @ehus

Add "popup" option to "rust_phantom_style"

Add "popup" option to "rust_phantom_style"

New documentation, unimplemented snippet, bug fixes

• documentation update
• Added context menu #222
• Add the unimplemented macro snippet #225
• replace after-operator with check for type declaration syntax #221