Remove omnisharp--filter-company-candidate

One of the completions being equal to the prefix is usually normal, and
removing it in the backend means idle completion will always try to
suggest completing to something, even if the current text is valid in
the current context.

If removing completions like this is somehow beneficial, it's probably
better performed in `company-transformers`.
company-omnisharp: use `annotation' instead of `crop'

Make use of text properties, they are handy for carrying extra
information.

`omnisharp--make-company-completion' still looks a bit suboptimal
(ideally, annotations would only be calculated when they're
displayed), but omnisharp doesn't seem to return huge completion lists
anyway.

Support for `crop' will be removed in company-mode 0.8, so this kind
of change is sort of mandatory.
Do some reformatting
Drop the auto-complete dependency

The popup.el dependency remains harder to cut out (for example,
`omnisharp-auto-complete-popup-keymap' references `popup-menu-keymap'
in its initvalue form).
Update the README
Add prompt for omnisharp-start-omnisharp-server
Allow starting OmniSharpServer via the graphical menu
Whitespace fixes
Document starting OmniSharpServer in emacs in README.md
Merge branch 'github-mgutekunst-master' into develop

This merge provides initial support for starting and managing an
OmniSharpServer instance inside emacs.
Fix message capitalization
Fix not caching OmniSharpServer path to correct variable

This could potentially fail, in, uh, some cases.
What.
Style changes

Setq returns the set value, so no need to use progn to group expressions
together.
Since if has no "else" expression, we should use (when)
Allow getting a shell command for executing OmniSharpServer

This works on different operating systems too.

Now with TESTS! Wow such professional.
Fix unable to start OmniSharpServer from emacs on osx

Also helps with omnisharp-reload-solution, which blocked emacs until the
command had completed on the server side. Now it doesn't block.
Remove syntax checking feature preview from README

It's not available due to changes in flycheck code, which is the actual
component handling the visual markerks and automation. I figured it's
not fair to advertise a feature this plugin doesn't even have.

See this ticket for investigation:

Latest version of Flycheck incompatible with Omnisharp checker · Issue
https://github.com/sp3ctum/omnisharp-emacs/issues/66
Bump version 1.7 -> 1.8
Merge branch 'develop'
Allow using a custom path to the curl program.

This allows using omnisharp-emacs without changing your PATH environment
variable to contain the directory for the curl executable.
Bump version 1.8 -> 1.9