Improve native WebAssembly compilation

[CryZe]

Here's the current state of native WebAssembly compilation. Everything is working except:

• Chrono doesn't compile. Improve native WebAssembly compilation #96 (comment)

[CryZe]

Looks like so far we are blocked by num not compiling due to rustc-serialize not compiling.

So we either have to wait for num to switch to serde rust-num/num#357
or rustc-serialize to actually merge rust-lang-deprecated/rustc-serialize#190 which seems actually pretty unlikely.

[CryZe]

With this PR chronotope/chrono#137 revived we could compile chrono on wasm too, we'd just need to bring our own Instant::now() and Utc::now()

[CryZe]

I began implementing this by not compiling the crates that don't work for the wasm target and polyfilling them. So that means mimicking relevant behavior (like parking_lot's locks being replaced by std's) and ignoring some other behavior for now (DateTimes are completely ignored, they are just empty structs)

[CryZe]

I got mostly everything working. Things that need to be fixed:

• Folder structure changed a bit, CI scripts need to be adjusted
• Instant::now()
• Basic Image Display
• PNG Decoding / Encoding
• Utc::now()
• Date Time calculations
• Basic Colors
• Color Conversions
• Bindings
• Hotkeys

[CryZe]

Looks like it was easy enough to just use the png crate to implement all the PNG Encoding / Decoding. So the only thing missing is chrono without the time dependency.

[CryZe]

Welp, it's actually somewhat broken. Whatever, at some point image will compile with the target, so I'm fine with that. It only really affects Llanfair files anyway.

[CryZe]

Nvm, turns out it was very easy to fix :)

[CryZe]

A recent upgrade of all the dependencies allowed us to get rid of all the polyfills except the one for chrono and the std::time stuff.