Remove Error-chain from examples not requiring it

[AndyGauge]

Per #502 these are identified as needing error-chain removed:

[ ] https://rust-lang-nursery.github.io/rust-cookbook/concurrency/threads.html#calculate-sha1-sum-of-iso-files-concurrently
[ ] https://rust-lang-nursery.github.io/rust-cookbook/cryptography/hashing.html#sign-and-verify-a-message-with-hmac-digest
[ ] https://rust-lang-nursery.github.io/rust-cookbook/cryptography/encryption.html#salt-and-hash-a-password-with-pbkdf2
[ ] https://rust-lang-nursery.github.io/rust-cookbook/datetime/parse.html#parse-string-into-datetime-struct
[ ] https://rust-lang-nursery.github.io/rust-cookbook/development_tools/debugging/log.html#log-messages-with-a-custom-logger
[ ] https://rust-lang-nursery.github.io/rust-cookbook/development_tools/debugging/log.html#log-to-the-unix-syslog
[ ] https://rust-lang-nursery.github.io/rust-cookbook/development_tools/versioning.html#parse-and-increment-a-version-string
[ ] https://rust-lang-nursery.github.io/rust-cookbook/development_tools/versioning.html#parse-a-complex-version-string
[ ] https://rust-lang-nursery.github.io/rust-cookbook/development_tools/versioning.html#check-if-given-version-is-pre-release
[ ] https://rust-lang-nursery.github.io/rust-cookbook/encoding/strings.html#percent-encode-a-string
[ ] https://rust-lang-nursery.github.io/rust-cookbook/encoding/strings.html#encode-and-decode-hex
[ ] https://rust-lang-nursery.github.io/rust-cookbook/encoding/csv.html#read-csv-records
[ ] https://rust-lang-nursery.github.io/rust-cookbook/encoding/csv.html#read-csv-records-with-different-delimiter
[ ] https://rust-lang-nursery.github.io/rust-cookbook/encoding/csv.html#handle-invalid-csv-data-with-serde
[ ] https://rust-lang-nursery.github.io/rust-cookbook/encoding/complex.html#serialize-and-deserialize-unstructured-json
[ ] https://rust-lang-nursery.github.io/rust-cookbook/encoding/complex.html#deserialize-a-toml-configuration-file
[ ] https://rust-lang-nursery.github.io/rust-cookbook/encoding/complex.html#read-and-write-integers-in-little-endian-byte-order
[ ] https://rust-lang-nursery.github.io/rust-cookbook/file/read-write.html#read-lines-of-strings-from-a-file
[ ] https://rust-lang-nursery.github.io/rust-cookbook/file/read-write.html#avoid-writing-and-reading-from-a-same-file
[ ] https://rust-lang-nursery.github.io/rust-cookbook/file/read-write.html#access-a-file-randomly-using-a-memory-map
[ ] https://rust-lang-nursery.github.io/rust-cookbook/net/server.html#listen-on-unused-port-tcpip
[ ] https://rust-lang-nursery.github.io/rust-cookbook/os/external.html#redirect-both-stdout-and-stderr-of-child-process-to-the-same-file
[ ] https://rust-lang-nursery.github.io/rust-cookbook/os/external.html#continuously-process-child-process-outputs
[ ] https://rust-lang-nursery.github.io/rust-cookbook/web/url.html#parse-a-url-from-a-string-to-a-url-type
[ ] https://rust-lang-nursery.github.io/rust-cookbook/web/url.html#create-new-urls-from-a-base-url
[ ] https://rust-lang-nursery.github.io/rust-cookbook/web/url.html#extract-the-url-origin-scheme--host--port
[ ] https://rust-lang-nursery.github.io/rust-cookbook/web/url.html#remove-fragment-identifiers-and-query-pairs-from-a-url
[ ] https://rust-lang-nursery.github.io/rust-cookbook/web/clients/apis.html#query-the-github-api
[ ] https://rust-lang-nursery.github.io/rust-cookbook/web/clients/apis.html#check-if-an-api-resource-exists
[ ] https://rust-lang-nursery.github.io/rust-cookbook/web/clients/apis.html#consume-a-paginated-restful-api

Essentially these recipes do not require error-chain because they do not require error variants. There is only one error type and no other error-chain identified feature used in these examples, and as such are easier to reason without hidden gotchas like an error handling library. Some of these needs the quick_main macro replaced with a well defined main function, that can be hidden.

[henrifrancois]

The current recipes for APIs under Clients up on the website are faulty as they omit the error_chain crate in the examples given. The extern crate was removed, but the behavior it induced was not, with Result<()> being prominent in these examples. The error_chain should either be added again, or removed properly this time