Update nickel dependency version

[Voltra]

According to the src folder in .cargo/registry, nickel_session@0.1.0 is dependent on nickel@0.8 which is dependent on mustache@0.6. Therefore, trying to cargo check a project that relies on it will give the following error message :

error: enum is private and its variants cannot be re-exported
  --> <cargo registry path>\mustache-0.6.3\src\parser.rs:4:9
   |
4  | pub use self::ParserState::*;
   |         ^^^^^^^^^^^^^^^^^^^^
...
43 | enum ParserState { TEXT, OTAG, TAG, CTAG }
   | ---------------- help: consider making the enum public: `pub enum ParserState`

error: enum is private and its variants cannot be re-exported
  --> <cargo registry path>\mustache-0.6.3\src\parser.rs:5:9
   |
5  | pub use self::TokenClass::*;
   |         ^^^^^^^^^^^^^^^^^^^
...
18 | enum TokenClass {
   | --------------- help: consider making the enum public: `pub enum TokenClass`

   Compiling gdi32-sys v0.2.0
error: aborting due to 2 previous errors

error: Could not compile `mustache`.

Modifying the dependency to nickel@0.10 should do the trick.

Information on my setup:

#rustc --version --verbose
rustc 1.32.0-nightly (4a45578bc 2018-12-07)
binary: rustc
commit-hash: 4a45578bc58ff262864f72680cc02e83f5d2f5b3
commit-date: 2018-12-07
host: x86_64-pc-windows-msvc
release: 1.32.0-nightly
LLVM version: 8.0

#cargo --version --verbose
cargo 1.32.0-nightly (5e85ba14a 2018-12-02)
release: 1.32.0
commit-hash: 5e85ba14aaa20f8133863373404cb0af69eeef2c
commit-date: 2018-12-02