Change syntax for env vars

[oanhnn]

In this Pull request, I will implement feature of issue #211
Change syntax for env vars to {{ ... }} and support allow whitespaces ( {{deploy_path}} and {{ deploy_path }} return same value).

Sorry by create other pull request.
This pull request is rebase of PR #218

[antonmedv]

Ok :)

[oanhnn]

Dear @Elfet ,
My pull request #219 has a problem.
With old parser (pattern /\{(.+?)\}/) detected all cases:

{abcxyz}
{abc-xyz}
{abc_xyz}
{abc.xyz}
{abc@zyx}

but new parser (pattern /\{\{\s*(\w+)\s*\}\}/) only detected cases:

{{abcxyz}}
{{abc_xyz}}

I can fix this, but i want specific requirements for env var.
I think we should only allow:

{{abcxyz}}
{{abc_xyz}}
{{abc.xyz}}

[gordalina]

I vote for same pattern as normal variables (implemented on #219).
Having a dot . on a variable could be used in the future to be a property of an array.

[oanhnn]

@gordalina, Is your attention?

env('abc', array('xyz' => 1));

echo env()->parse('{{abc.xyz}}');

output:

1

[gordalina]

I didn't know about parse.
Still, I keep my opinion, and would suggest making parse() private and env() would call parse() here

This way, properties are part of the DSL and the user doesn't need to know wether it is necessary to parse them or not.

What are your thoughts @oanhnn @Elfet?

[oanhnn]

I think:

1. Method parse will be private. It is only call when using run().
2. When call env($abc, $xyz) or env()->set($abc, $xyz), variable $abc will check and only allow a-z, A-Z, 0-9 and underscore character ( _ )
3. When call env($abc) or env()->get($abc), variable $abc will check and only allow a-z, A-Z, 0-9, underscore character ( _ ) and dot character ( . ) . If having a dot on variable $abc could be used in the future to be a property of an array.

[gordalina]

@oanhnn exactly!