Make completion context aware

[kritzcreek]

eg. ghc-company has these contexts:

https://github.com/iquiw/company-ghc/blob/master/company-ghc.el#L150-L174

From the top of my head I can think about these possible contexts:

• Import
• Type declaration
• Record (If we could figure out the type of the record in question it would be nice to provide fields for that record type)
• Qualified completion
• normal completion

[dbushenko]

@kritzcreek Please split those into separate issues.

[rexim]

@kritzcreek please do not use blob links. The file was changed significantly since September 13, and now I see something weird there.

Here is the correct link: https://github.com/iquiw/company-ghc/blob/cf257eead917df31a846807bee99468f2d4585fe/company-ghc.el#L150-L174

Small Tip: when you are looking at some file on GitHub, just press y and you will get redirected from the blob link to the current commit link.

[kritzcreek]

@rexim thanks for the tip! I'll certainly start using that